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## "Available"

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ABSTRACT:

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Colloquium
Friday, November 18, 2022
3:30 PM
Clark Hall, Room 108

## "You have your physics results. Now what?"

Sami Mitra , PRL
[Host: Avik Ghosh]
ABSTRACT:

In a talk that I am hoping will quickly morph into a free-flowing Q and A session, I will discuss the roles of journals in general and PRL in particular in disseminating physics results through a cascading sequence involving journal editors, referees, conference chairs, journalists, department chairs, deans, funding agencies, and others. While some of the essential tools of physics dissemination are unchanged, the arrival of social media, search engines, and electronic repositories have us in a state of flux.

Colloquium
Friday, November 11, 2022
2:00 PM
Thornton, Room 303

 Available ABSTRACT: Available Colloquium Friday, November 11, 2022 2:00 PM Clark Hall, Room 108  Add to your calendar

## "Available"

Available
ABSTRACT:

Available

Colloquium
Friday, November 4, 2022
3:30 PM
Clark Hall, Room 108

## "Available"

Available
ABSTRACT:

Available

Colloquium
Friday, October 28, 2022
3:30 PM
Clark Hall, Room 108

## "Available"

Available
ABSTRACT:

available

Colloquium
Friday, October 21, 2022
3:30 PM
Clark Hall, Room 108

## "The Heavyweight W boson - an Upset to the Standard Model of Particle Physics"

Ashutosh Kotwal , Duke University
[Host: Craig Group]
ABSTRACT:

The Standard Model of particle physics has been a crowning achievement of fundamental physics, culminating in the discovery of the Higgs boson in 2012. As a quantum theory of the building blocks of matter and forces, it has been one of the most successful theories in science. The recent measurement of the mass of the W boson disagrees with the theory prediction. This upset to the Standard Model may point towards exciting new discoveries in particle physics in the coming years. We will discuss the Standard Model, the crucial role of the W boson, and how it has become the harbinger of new laws of nature.

Colloquium
Friday, October 14, 2022
3:30 PM
Clark Hall, Room 108

https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

## "Enhanced associative memory, classification and learning with active dynamics"

Suri Vaikuntanathan , University of Chicago
[Host: Marija Vucelja ]
ABSTRACT:

Motivated by advances in the field of active matter where non-equilibrium forcing has been shown to activate new assembly pathways, here we study how  non-equilibrium driving in prototypical   memory formation models  can affect their information processing capabilities. Our results reveal that activity can provide a new and surprisingly general way to dramatically improve the memory and information processing performance of the above described systems without the need for additional interactions or changes in connectivity. Non-equilibrium dynamics can allow these systems to have memory capacity, assembly or pattern recognition properties, and learning ability, in excess of their corresponding equilibrium counterparts. Counter-intuitively, in some cases, dynamics with non-equilibrium noise-sources can even have a higher memory capacity than  zero temperature equilibrium systems that are not subject to any noise.  Our results demonstrate the  generality of the enhancement of memory capacity arising from non-equilibrium, active dynamics. These results are of significance to a variety of processes that take place under nonequilibrium dynamics, and involve information storage and retrieval, as well as in silico learning and memory forming systems for which nonequilibrium dynamics may provide an approach for modulating memory formation.

Colloquium
Friday, October 7, 2022
3:30 PM
Clark Hall, Room 108

https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

## "Available"

Available
ABSTRACT:

available

Colloquium
Friday, September 30, 2022
3:30 PM
Clark Hall, Room 108

## "What is hiding beyond the Standard Model?"

Craig Group , UVA - Department of Physics
[Host: Despina Louca]
ABSTRACT:

During the last century, particle physicists have formulated and tested a “Standard Model” of fundamental particle physics.  This model has been extremely valuable in successfully making precise predictions for thousands of experiments.  Still, physicists know this model is incomplete!  For example, through many astrophysical observations, we know that the source of a large fraction of the energy in the Universe is due to particles and forces beyond what is included in the Standard Model.  This is a pretty big missing piece, but there is more!  We also don’t understand the structure of the Standard Model, or the reason we observe a matter-dominated Universe – why not antimatter?  These mysteries (and others) mean that there is certainly “New Physics” waiting to be discovered if we do the right experiments!  Where is the New Physics hiding?  We don’t know.  I’ll review several ongoing experimental efforts aimed at answering some of these big fundamental mysteries.

VIDEO:
Colloquium
Friday, September 23, 2022
3:30 PM
Clark Hall, Room 108

https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

## "Gravitational Waves as a Probe of Fundamental Physics and Astrophysics"

Kent Yagi , UVA-Department of Physics
[Host: Despina Louca]
ABSTRACT:

Recent observations of black holes and neutron stars through gravitational waves allow us to explore the novel strong-gravity and extreme-density regime. In this talk, I will explain how we can use gravitational waves from binary black hole mergers to probe gravitational physics and those from binary neutron star mergers to study nuclear physics. For the former, I will focus on a theory beyond General Relativity motivated by string theory while for the latter, I will investigate the presence of solid quark cores inside neutron stars. I will also comment on how we can use gravitational waves from binary white dwarfs, expected to be detected with future space-based detectors, to learn astrophysics.

VIDEO:
Colloquium
Friday, September 16, 2022
3:30 PM
Clark Hall, Room 108

https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

## "Pursuit of Equity and Excellence in the APS Division of Nuclear Physics"

Warren Rogers , Indiana Wesleyan University
[Host: Simonetta Liuti]
ABSTRACT:

TBA

Colloquium
Friday, September 9, 2022
3:30 PM
Clark Hall, Room 108

## "Atom Interferometry on Earth and in Space"

Cass Sackett , UVA - Department of Physics
[Host: Despina Louca]
ABSTRACT:

Atom interferometers are a type of quantum sensor useful for navigation, geographics, and tests of fundamental physics. We report on recent progress in three areas: a trapped-atom Sagnac interferometer for rotation sensing, the use of atom interferometry to measure "tune-out wavelengths," and a demonstration of atom interferometry in the Cold Atom Laboratory on the ISS. These efforts are representative of the types of efforts begin pursued in the field, including pushing towards practical applications, pursuing basic science, and technology demonstrations to support future applications and science.

VIDEO:
Colloquium
Friday, September 2, 2022
3:30 PM
Clark Hall, Room 108

https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

## "Available"

Available
ABSTRACT:

available

Colloquium
Friday, August 26, 2022
3:30 PM
Clark Hall, Room 108

## "Re-inventing fixed-target experiments to probe light dark matter"

Cristina Mantilla , Fermilab
[Host: Dustin Keller]
ABSTRACT:

The search for dark matter is ever-evolving and a number of experiments are underway to search for the constituents of dark matter across a vast range of masses. A largely unexplored regime is that where light dark matter particles, with masses between the electron and proton masses, may interact feebly with ordinary matter. I will discuss how small accelerator experiments can produce these dark matter candidates by scattering energetic particles on a fixed target. I will focus on the DarkQuest experiment at Fermilab that uses a proton beam and builds off of an existing detector and accelerator infrastructure. I will also describe how an electron beam can be complimentary used in the Light Dark Matter experiment (LDMX) at SLAC. I will explain the design and challenges of these experiments and their prospects for characterizing a dark matter signal in the near future.

Colloquium
Friday, April 29, 2022
3:30 PM
Ridley Hall, Room G008

## "Probing the Universe with Gravitational Waves"

Barry C. Barish , Professor of Physics, Emeritus, at Caltech, and Distinguished Professor of Physics, at UC Riverside, Nobel Laureate 2017
ABSTRACT:

The discovery of gravitational waves, predicted by Einstein in 1916, is enabling both important tests of the theory of general relativity, and represents the birth of a new astronomy. Modern astronomy, using all types of electromagnetic radiation, has giving us an amazing understanding of the complexities of the universe, and how it has evolved. Now, gravitational waves and neutrinos are beginning to provide the opportunity to pursue some of the same astrophysical phenomena in very different ways, as well as to observe phenomena that cannot be studied with electromagnetic radiation. The detection of gravitational waves and the emergence and prospects for this exciting new science will be explored.

VIDEO:
Colloquium
Monday, April 25, 2022
7:00 PM
Newcomb Hall, Room Newcomb Hall Theater

Hoxton Lecture

## "The expansion of space, a scaling symmetry, and a mirror-world dark sector"

Professor Lloyd Knox , UC Davis
[Host: Prof. Genya Kolomeisky]
ABSTRACT:

I will introduce, for those unfamiliar with general relativity, the notion of the expansion of space, before going on to discuss a 5 sigma discrepancy between two inferences of the rate of that expansion today. One of those inferences is highly indirect and model dependent, relying on measurements of maps of the cosmic microwave background (CMB), a thermal relic of the hot big bang. I will explain what the CMB is, and show how well our standard cosmological model describes its statistical properties, and how we can use that model to infer the expansion rate today. I will then describe a symmetry under a scaling transformation of all relevant time scales in the problem that can potentially be exploited to reconcile the two inferences. Significant constraints on such a solution come from measurements of the CMB energy density and the abundances of light elements produced in the big bang. The former constraint can be circumvented by use of a ‘mirror world’ dark sector — a copy of the standard model of particle physics with little to no interactions with standard model particles other than via gravity.

Colloquium
Friday, April 22, 2022
3:30 PM
Ridley Hall, Room G008

Joint Physics-Astronomy colloquium

##### Attend virtually via Zoom:   https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Available
Colloquium
Friday, April 15, 2022
3:30 PM
Ridley Hall, Room G008

## "Electron spin resonance spectroscopy of quantum spin liquids"

Oleg Starykh , The University of Utah, Salt Lake City
[Host: Prof. Dima Pesin]
ABSTRACT:

Much of the current research in quantum magnetism is motivated by the search for an elusive quantum spin liquid (QSL) state of the magnetic matter. A salient feature of this entangled quantum state is the presence of fractionalized elementary excitations such as spin-1/2 spinons, interactions between which are mediated by the emergent gauge field.

In my talk, I provide a historical perspective on quantum spin liquids and shed some light on the origins of  this weird” idea. Following a brief summary of the current state of affairs in QSL research, I describe  how QSLs respond to the magnetic field and demonstrate surprising similarity of the described response to that of neutral Fermi liquids.

I illustrate these theoretical ideas with a recent electron spin resonance measurements on quasi-one-dimensional antiferromagnet K2CuSO4Br2. The experiment leads the first-ever spectroscopic determination of the (backscattering) interaction between spinon excitations of the quantum spin chain.

VIDEO:
Colloquium
Friday, April 8, 2022
3:30 PM
Ridley Hall, Room G008

## "How to Become a More Effective Mentor/Mentee"

Kirsten Tollefson , Professor and Associate Dean, Graduate School, at Michigan State University
[Host: Prof. Craig Group]
ABSTRACT:

I will discuss what recent research says about the science of effective mentorship and how we can learn to do it better. We will focus on 2 competencies - aligning expectations and maintaining effective communication - through some guided activities. I will give you examples of strategies and resources that can help you become a more effective mentor and mentee.

VIDEO:
Colloquium
Friday, April 1, 2022
3:30 PM
Ridley Hall, Room G008

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Available
Colloquium
Friday, March 25, 2022
3:30 PM
Ridley Hall, Room G008

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Available
Colloquium
Friday, March 18, 2022
3:30 PM
Ridley Hall, Room G008

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

SPRING BREAK
Colloquium
Friday, March 11, 2022
3:30 PM
Ridley Hall, Room G008

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

 Available Colloquium Friday, March 4, 2022 3:30 PM Ridley Hall, Room G008  Add to your calendar

## "A Career Outside the Academia: My Experiences as VP at a small Hi Tech Company"

Dr. Zuyu Zhao , Janis ULT Inc.
[Host: Prof. Bellave Shivaram]
ABSTRACT:

Most of the physics students will work in industry instead of academia after they got the degree (BSc., MS, or Ph.D.)

The speaker will share his personal 30 year experience of working in a small tech company after his post-doc period, including changes and challenges of culture, daily life, responsibilities, etc.

Advice will be discussed with the audience how meet the challenges.

The speaker’s main tasks were to develop ultra-low temperature facilities from 300mK to 10mK. Along with the speaker’s career growth, examples of his achievements are presented.

A brief business summary of the speaker’s company, before and after COVID, is presented at the end of the presentation.

Colloquium
Friday, February 25, 2022
3:30 PM
Online, Room via Zoom

## "Failure to Social Distance: Breaking Gathering Limits in Titan's Lakes"

Alex Rosenthal , University of Virginia - Department of Physics
[Host: Stefan Baessler]
ABSTRACT:

Saturn's moon Titan is a geologically and meteorologically active world seen as a potential location for the development of life. While we cannot immediately answer "Is there life on TItan?" or even "Are there life-forming reactions occurring?" we can take a step back and investigate a more foundational question: "What chemistries are occurring?" The answers to this question are stepping stones to understanding broader processes such as weather cycles, geology, and potentially organic reactions. We attack this question using molecular dynamics simulations. By identifying molecules that cluster or exhibit other interesting behaviors, we hope to identify possible sites for interesting chemical reactions that could produce large or prebiotic molecules, as well as characterize those reactions.

Colloquium
Friday, February 18, 2022
3:30 PM
Ridley Hall, Room G008

## "Coordinate Space Representation and Average Radius of Quark and Gluon Generalized Parton Distribution Functions"

Zaki Panjsheeri , University of Virginia - Department of Physics
[Host: Stefan Baessler]
ABSTRACT:

The task of the field of nuclear physics called femtography is to image the internal structure of strongly interacting particles, from single protons and neutrons to atomic nuclei. Protons and neutrons are composed of quarks and gluons, but the precise spatial arrangement of the two valence up quarks and one valence down quark, along with the sea quarks and gluons that contribute half of the momentum, remains unknown.  A compelling method for deriving dynamical information about the internal structure of the proton is through the use of generalized parton distributions (GPDs).  Two-dimensional Fourier transforms of GPDs provide insight into matter, charge, and radial distributions of the quarks and gluons inside the nucleon.  We present an explicit calculation of such transforms in a spectator model framework using parametric analytic forms of GPDs, originally constrained using deeply virtual Compton scattering and lattice QCD data.  We compare the valence quarks to the gluon distribution through, i.a., average radii, a notion of distance inside the nucleon, and we present a novel result for the radius of the gluon density.

Colloquium
Friday, February 18, 2022
3:50 PM
Ridley Hall, Room G008

## "Property Tuning of Layered Materials by Electrochemical Intercalation"

Dawn Ford , University of Virginia - Department of Physics
[Host: Stefan Baessler]
ABSTRACT:

Recent developments in two-dimensional (2D) magnetism have intensified the research on novel van-der Waals magnetic materials to explore new magnetic phenomena in the 2D limit. Among 2D magnetic materials, one model system is metal thiophosphates MPX3 (M = transition metal ions, X = chalcogen ions) in which the antiferromagnetic (AFM) properties are highly dependent on the choice of transition metal M. The van der Waals-type crystal structure allows the mechanical exfoliation of bulk crystals to obtain atomically thin layers. In MPX3, the AFM ordering is found to persist down to the atomically thin limit, making them a promising candidate for future device applications. Furthermore, the layered structure also permits the inter-layer intercalation, which is an effective way to tune the properties. With this motivation, we performed Li and Fe intercalation in NiPS3 by using electrochemical technique. In this method, the electrical potential causes electrons to flow from anode to cathode through the circuit within the battery leading to the intercalation of intercalant ions between the layers of the host sample as shown in figure below. By tuning the amount of charges intercalated during electrochemical intercalation, the number of intercalated ions in the host single crystal can be controlled. NiPS3 exhibits AFM ordering below TN = 155 K and the spin-flop transition above μ0H ≈ 6 T. The goal of this project is to intercalate different Li and Fe content in NiPS3 single crystals and characterize their magnetic properties. Mainly, we will focus on the tuning of the ordering temperature and the spin-flop field of pristine NiPS3. In addition, the transition from AFM state to other states such as ferromagnetism is also one important direction of this project. Li intercalation was found to increase the magnetization value of NiPS3.  Future work will consist of characterizing the changes in the magnetic ordering of Fe intercalated NiPS3 and extending the investigation of Li intercalated NiPS3.

Colloquium
Friday, February 18, 2022
4:10 PM
Ridley Hall, Room G008

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Available
Colloquium
Friday, February 11, 2022
3:30 PM
Ridley Hall, Room G008

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

 Available Colloquium Friday, February 4, 2022 3:30 PM Ridley Hall, Room G008  Add to your calendar

## "Artificial Intelligence in Spin Physics"

Dustin Keller , University of Virginia - Department of Physics
[Host: Despina Louca]
ABSTRACT:

The landscape of physics research is changing due to the rapid advancement in computing. Traditionally, science is done through observation and experimentation.  While there is no indication yet that this trend will change overnight, there is an increasing likelihood that methods in physics are changing in a way that we must prepare for. New technology, new methods, and new instrumentation must be brought to the forefront to take advantage of the rapid evolution of artificial intelligence and its ubiquitous pervasiveness in all aspects of research and life.  I briefly review some of the advancement in machine learning and how these developments are changing our field using examples in Spin Physics from the recent past, the present, and near the future.

VIDEO:
Colloquium
Friday, January 28, 2022
3:30 PM
Online, Room via Zoom

## "Studying matter and spacetime with gravitational waves"

Professor David Nichols , University of Virginia - Department of Physics
[Host: Professor Despina Louca]
ABSTRACT:

Gravitational waves have been detected from the mergers of nearly ninety binary black holes during the first three observing runs of the Advanced LIGO and Virgo detectors. In this talk, I will discuss these detections and their implications for understanding fundamental properties of matter and spacetime in two contexts. First, I will review a nonlinear effect in general relativity called the gravitational-wave memory. The effect is characterized by a lasting change in the gravitational-wave strain produced by the energy radiated in gravitational waves. I will describe how this effect is related to the infrared properties of gravity, how the memory effect can be measured with LIGO and Virgo, and how new types of memory effects have been recently predicted. Second, I will discuss how dense distributions of dark matter around a black hole can influence the inspiral of a second compact object and thus the gravitational waves emitted from such a binary. With the planned space-based gravitational-wave detector LISA, the distribution of dark matter on these small scales could be mapped precisely. This would provide a new method to study dark matter: with gravitational waves.

VIDEO:
Colloquium
Friday, January 21, 2022
3:30 PM
Physics Building, Room 204

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Available
Colloquium
Friday, December 10, 2021
3:30 PM
Physics Building, Room 204

## "Floquet-engineering topological Dirac bands in an optical lattice"

Ian Spielman , NIST and The University of Maryland
[Host: Prof. Dima Pesin]
ABSTRACT:

Over the years my group has performed a number of experiments realizing relativistic physics using cold atoms — described by the 1D Dirac Hamiltonian in some degree of approximation.  I will begin by reviewing these results in conjunction with those from the whole of the cold-atom community.

With that backdrop, I describe a spin dependent bipartite Floquet lattice, in which the dispersion relation is linear for all points in the Brillouin zone. The (stroboscopic) Floquet spectrum of our periodically-driven Hamiltonian features perfect spin-momentum locking, and a linear Dirac dispersion.  These bands are protected by a Floquet topological invariant which we directly measure by using quantum state tomography.

VIDEO:
Colloquium
Friday, December 3, 2021
3:30 PM
Physics Building, Room 204

## "Analogue gravity in cold atom and condensed matter systems "

Professor Daniel Sheehy , Louisiana State University
[Host: Cass Sackett]
ABSTRACT:

In recent years there has been much interest in the field of "analogue gravity", in which cosmological or astrophysical phenomena like Hawking radiation are mimicked in a laboratory experiment.  At LSU, my research group in cold atom/condensed matter theory became interested in this field, motivated by the recent experiment of Eckel and collaborators, [Phys. Rev. X 8, 021021 (2018)] who used a rapidly expanding Bose-Einstein condensate (BEC) to reproduce the inflationary regime of the early universe.  I will present our work on the physics of inflation in expanding BEC's, and discuss other setups to detect analogue gravity phenomena like the Unruh effect.

VIDEO:
Colloquium
Friday, November 19, 2021
3:30 PM
Physics Building, Room 204

## "Physics motivations for future colliders"

Professor Tao Han , University of Pittsburg
[Host: Professor P.Q. Hung]
ABSTRACT:

With the milestone discovery of the Higgs boson at the CERN Large Hadron Collider (LHC), high energy physics has entered a new era. The completion of the “Standard Model” (SM) implies, for the first time ever, that we have a relativistic, quantum-mechanical, self-consistent theoretical framework, conceivably valid up to exponentially high energies, even to the Planck scale. Yet, the SM leaves many unanswered questions both from the theoretical and observational perspectives, including the nature of the electroweak superconductivity and its phase transition, the hierarchy between the particle masses and between the observed scales, the nature of dark matter etc. There are thus compelling reasons to believe that new physics beyond the SM exists. We argue that the collective efforts of future high energy physics programs, in particular the future colliders, hold great promise to uncover the laws of nature to a deeper level.

VIDEO:
Colloquium
Friday, November 12, 2021
3:30 PM
Physics Building, Room 204

## "Atomtronics for Quantum Sensing"

Professor Malcolm Boshier , Los Alamos National Lab
[Host: Prof. Cass Sackett]
ABSTRACT:

Atomtronics is the emerging technology of building circuits where the current is a flow of ultracold atoms propagating as coherent matter waves inside suitable waveguides.  In this talk I will describe our atomtronic technology in which the waveguides are created with laser light via the optical dipole potential, and then discuss two quantum sensors based on it.  First, we have demonstrated the atomtronic analogue of the dc SQUID and shown that it exhibits the quantum interference that gives the Superconducting Quantum Interference Device its name.   In the conventional SQUID this is seen as a periodic variation of critical current with magnetic flux.  In the atomtronic SQUID it causes a periodic variation of critical current with rotation, enabling the device to function as a gyro.  Second, we are developing an atomtronic version of the Fiber Optic Gyro, in which rotation is measured by the Sagnac effect.  In our device a Bose-Einstein condensate is split, reflected, and recombined inside a waveguide that is translated so that the wavepackets travel around a loop and realize a waveguide Sagnac atom interferometer.

Colloquium
Friday, November 5, 2021
3:30 PM
Physics Building, Room 204

## "Exploring Gravitational Wave and Dark Matter Physics with the 100-meter-tall MAGIS-100 Atom Interferometer"

Professor Tim Kovachy , Northwestern University
[Host: Prof. Bob Hirosky]
ABSTRACT:

Atom interferometers exploit spatially delocalized quantum states to make a wide variety of highly precise measurements.  Recent technological advances have opened a path for atom interferometers to contribute to multiple areas at the forefront of modern physics, including searches for wave-like dark matter, gravitational wave detection, and fundamental quantum science.  In this colloquium, I will describe MAGIS-100, a 100-meter-tall atom interferometer being built at Fermilab to pursue these directions.  MAGIS-100 will serve as a prototype gravitational wave detector in a new frequency range, between the peak sensitivities of LIGO and LISA, that is promising for pursuing cosmological signals from the early universe and for studying a broad range of astrophysical sources.  In addition, MAGIS-100 will search for wave-like dark matter, probe quantum mechanics in a new regime in which massive particles are delocalized over macroscopic scales in distance and time, and act as a testbed for advanced quantum sensing techniques.  Finally, I will discuss the potential and motivation for follow-on atomic detectors with even longer baselines.

VIDEO:
Colloquium
Friday, October 29, 2021
3:30 PM
Physics Building, Room 204

## "Quantum Many-Body Physics of Superconducting Qubits"

Professor Leonid Glazman , Yale University
[Host: Dima Pesin]
ABSTRACT:

The ongoing development of superconducting qubits has brought some basic questions of many-body physics to the research forefront, and helped solve several of them. I will address two effects in quantum condensed matter highlighted by the development of a fluxonium qubit. The first one is the so-called cosine-phi problem stemming from the seminal paper of Brian Josephson. It predicted the phase dependence of the dissipative current across the Josephson junction. A fluxonium qubit enabled the observation of the effect, after nearly 50 years of unsuccessful attempts by other techniques. The second one is inelastic scattering ("splitting") of a microwave photon by quantum fluctuations of phase across a Josephson junction. This effect is the elementary mechanism driving the Schmid transition, which predicts a collapse of the Josephson current in a junction influenced by a dissipative environment.

VIDEO:
Colloquium
Friday, October 22, 2021
3:30 PM
Physics Building, Room 204

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Available
Colloquium
Friday, October 15, 2021
3:30 PM
Physics Building, Room 204

## " Muon magnetic anomaly: probing the innermost nature of vacuum"

Professor Dinko Pocanic , University of Virginia - Department of Physics
[Host: Prof. Gordon Cates]
ABSTRACT:

Marking the semi-anniversary of the Fermilab Muon g−2 experiment (E989) Run 1 result, this colloquium will review the current status of the muon magnetic anomaly, the inferred evidence of possible particles outside the Standard Model (SM), and future prospects in this active research field.

The intrinsic magnetic field of a simple object, such as a compass needle, is expressed in terms of its magnetic moment.  The magnetic moment of a point particle, such as the electron, is predicted by relativistic quantum mechanics to be g = 2, in convenient dimensionless units.  For the electron, this prediction fails at the part-per-thousand level; the resulting magnetic anomaly, ae = (g − 2)/2, is due to the electron’s couplings to virtual particles excited in the vacuum.

Muon, the electron’s 200 times heavier cousin, experiences far stronger couplings to massive virtual particles, including possible non-SM exotics. The SM provides a prediction for the muon magnetic anomaly aµ with sub-ppm precision. Hence, a comparably precise measurement of aµ offers a uniquely sensitive test for the presence of non-SM particles in nature. For almost 20 years a tantalizing discrepancy of ∼ 3 – 4σ has persisted between the measurements of aµ, and the SM calculations. The Fermilab Muon g−2 Run 1 result brings a much awaited update to this test, with much more to come.

VIDEO:
Colloquium
Friday, October 8, 2021
3:30 PM
Physics Building, Room 204

## "Rotation sensing with an atom-interferometer gyroscope"

Professor Cass Sackett , University of Virginia - Department of Physics
[Host: Gordon Cates]
ABSTRACT:

Precision rotation sensing is useful for navigation, geophysics, and tests of fundamental physics. Atom interferometers provide, by some measures, the most sensitive method for rotation sensing achieved to date. However, the best performance requires freely falling atoms in a large experimental apparatus. Many applications, such as navigating a vehicle, will benefit from a more compact geometry. One method to achieve this is by using trapped atoms that are suspended against gravity. We have implemented such an interferometer and used it to measure a rotation rate comparable to that of the Earth. The most recent iteration of the interferometer has demonstrated improvements by a factor of ten in rotation sensitivity and trap stability. A second new apparatus reduces the scale of the vacuum chamber and optical system to roughly the size of a microwave oven.

VIDEO:
Colloquium
Friday, October 1, 2021
3:30 PM
Physics Building, Room 204

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Available
Colloquium
Friday, September 24, 2021
3:30 PM
Physics Building, Room 204

## "Inside the Proton: science fact, speculation, and the stuff of science fiction"

Professor Gordon Cates , University of Virginia - Department of Physics
[Host: Kent Paschke]
ABSTRACT:

Whereas the structure of the atom has been  understood for many years, the internal structure of the proton (and neutron) is the subject of active research.  Understanding the nucleon is difficult because its structure is governed by quantum chromodynamics, or QCD, which has not been solved exactly in the non-perturbative or low-energy regime.  The proton's structure is intriguing, however, for many reasons.  For example, we think of the proton as being made of three quarks, but the mass of those quarks only accounts for about 1% of the proton's mass.  The remaining 99%, and hence 99% of the known mass in the universe, is due to exotic effects associated with the QCD vacuum.  While a great deal of work remains to be done, the way in which we visualize the proton has changed dramatically since the discovery of quarks.  Just as the structure of the atom was unveiled early in the 20th century, the structure of the proton is being unveiled in the first decades of the 21st century.  Another intriguing aspect of the proton arises from the fact that QCD is the only theory in nature that has essentially no free parameters. String theory, that attempts to unify our understanding of gravity and the quantum world, grew out of early efforts to understand the strong interaction.  Since string theory deals with the topology of space and time, it is tempting to believe that a deep understanding of the proton may one day provide a window into even more fundamental questions. The colloquium will cover some recent developments in our understanding of the nucleon, as well as providing a glimpse of where this rich area of research is heading in upcoming years.

VIDEO:
Colloquium
Friday, September 17, 2021
3:30 PM
Physics Building, Room 204

## "Stirring by staring: Induced non-equilibrium states by measurements in quantum systems"

Israel Klich , University of Virginia - Department of Physics
[Host: Despina Louca]
ABSTRACT:

In quantum mechanics, the role of an observer is fundamentally different from that of a classical observer.  The quantum mechanical observer necessarily plays an active role in the dynamics of the system that it is observing.  This apparent difficulty may be turned into a tool to drive an initially trivial system into a complicated quantum many-body state simply by observing it.  I will present two remarkable examples of states induced by measurement. In the first, we examine the role of a moving density measuring device interacting with a system of fermions, and in particular, show that it would leave behind a wake of purely quantum origin. In the second example, inspired by the recent invention of topological Floquet insulators, we will see how a suitably chosen set of density measurements, repeated periodically, will induce robust chiral edge motion on a lattice of free fermions. Our examples show how quantum mechanical observation can be added as a versatile tool to the arsenal of quantum engineering in condensed matter systems.

VIDEO:
Colloquium
Friday, September 10, 2021
3:30 PM
Physics Building, Room 204

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Available
Colloquium
Friday, September 3, 2021
3:30 PM
Physics Building, Room 204

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Available
Colloquium
Friday, August 27, 2021
3:30 PM
Physics Building, Room 204

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

 Available Colloquium Friday, April 30, 2021 3:30 PM Online, Room via Zoom  Add to your calendar
 Available Colloquium Friday, April 23, 2021 3:30 PM Online, Room via Zoom  Add to your calendar
 Available Colloquium Friday, April 16, 2021 3:30 PM Online, Room via Zoom  Add to your calendar
 Available Colloquium Friday, April 9, 2021 3:30 PM Physics Building, Room TBA  Add to your calendar
 Available Colloquium Friday, April 2, 2021 3:30 PM Physics Building, Room TBA  Add to your calendar
 Available Colloquium Friday, March 26, 2021 3:30 PM Physics Building, Room TBA  Add to your calendar
 Available Colloquium Friday, March 19, 2021 3:30 PM Physics Building, Room TBA  Add to your calendar
 RESERVED Colloquium Friday, March 12, 2021 3:30 PM Physics Building, Room Online  Add to your calendar
 RESERVED Colloquium Friday, March 5, 2021 3:30 PM Physics Building, Room TBA  Add to your calendar
 Available Colloquium Friday, February 26, 2021 3:30 PM Physics Building, Room TBA  Add to your calendar
 RESERVED Colloquium Friday, February 19, 2021 3:30 PM Online, Room via Zoom  Add to your calendar

## "Complexity of magnetic patterns and self-induced spin-glass state"

Prof. Mikhail Katsnelson , Radboud University of Nijmegen, The Netherlands,
[Host: Dima Pesin]
ABSTRACT:

The origin of complexity remains one of the most important and, at the same time, the most controversial scientific problems. Earlier attempts were based on theory of dynamical systems but did not lead to a satisfactory solution of the problem. I believe that a deeper understanding is possible based on a recent development of statistical physics, combining it with relevant ideas from evolutionary biology and machine learning.

Using patterns in magnetic materials as the main example, I discuss some general problems such as (a) a formal definition of pattern complexity [1]; (b) self-induced spin glassiness due to competing interactions as a way to interpret chaotic patterns [2]; (c) multi-well states intermediate between glasses and ordinary ordered states and their relevance for the problem of long-term memory in complicated systems [3]; and (d) complexity of frustrated quantum spin systems [4]. I will also review a very recent experimental observation of self-induced spin-glass state in elemental neodymium [5].

[1] A. A. Bagrov, I. A. Iakovlev, A. A. Iliasov, M. I. Katsnelson, and V. V. Mazurenko, Multi-scale structural complexity of natural patterns, PNAS 117, 30241 (2020).
[2] A. Principi and M. I. Katsnelson, Spin glasses in ferromagnetic thin films, Phys. Rev. B 93, 054410 (2016); Self-induced glassiness and pattern formation in spin systems due to long-range interactions, Phys. Rev. Lett. 117, 137201 (2016).
[3] A. Kolmus, M. I. Katsnelson, A. A. Khajetoorians, and H. J. Kappen, Atom-by-atom construction of attractors in a tunable finite size spin array, New J. Phys. 22, 023038 (2020).
[4] T. Westerhout, N. Astrakhantsev, K. S. Tikhonov, M. I. Katsnelson, and A. A. Bagrov, Generalization properties of neural network approximations to frustrated magnet ground states, Nature Commun. 11, 1 (2020).
[5] U. Kamber et al, Self-induced spin glass state in elemental and crystalline neodymium, Science 368, eaay6757 (2020).
VIDEO:
Colloquium
Friday, February 12, 2021
2:00 PM
Online, Room via Zoom

## "A fermionic triangular-lattice quantum gas microscope "

Peter Schauss , University of Virginia - Physics Dept.
[Host: Bob Jones]
ABSTRACT:

Geometrically frustrated many-body systems show many interesting emerging phenomena, ranging from kinetic frustration to exotic spin ordering and chiral spin liquid phases. Ultracold atom systems offer great tunability and flexibility to realize such systems in a wide parameter range of interactions, densities, and spin-imbalance.

In this talk, I will present our recent results on site-resolved imaging of ultracold fermionic lithium atoms on a triangular optical lattice.

Degenerate Fermi gases with about one tenth of the Fermi temperature have been realized within a crossed dipole trap and successfully loaded into a two-dimensional triangular optical lattice. To characterize this lattice, we observed Kapitza-Dirac scattering using a molecular Bose-Einstein condensate. Collecting the emitted photons during Raman sideband cooling in the triangular lattice using a high-resolution microscope objective enabled the high-fidelity imaging of individual fermionic atoms in the lattice with single-site resolution.

The next step will be the realization of a triangular lattice Hubbard model by implementing an additional optical lattice to increase interactions.

This novel experimental platform will allow us to study spin and density correlations in the triangular Hubbard model to explore signatures of frustration and spin-hole bound states and may lead to a direct observation of non-vanishing chiral correlations.

VIDEO:
Colloquium
Friday, February 5, 2021
3:30 PM
Physics Building, Room via Zoom

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

 Available Colloquium Friday, November 20, 2020 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, November 13, 2020 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, October 30, 2020 3:30 PM Physics Building, Room 204  Add to your calendar

## "Bosonic Quantum Information Processing with Superconducting Circuits"

Professor Liang Jiang , Pritzker School of Molecular Engineering, University of Chicago
[Host: Olivier Pfister]
ABSTRACT:

Bosonic modes are widely used for quantum communication and information processing. Recent developments in superconducting circuits enable us to control bosonic microwave cavity modes and implement arbitrary operations allowed by quantum mechanics, such as quantum error correction against excitation loss errors. We investigate different bosonic encoding and error correction protocols, and provide a perspective on using bosonic quantum error correction for various applications.

VIDEO:
Colloquium
Friday, October 23, 2020
3:30 PM
Online, Room via Zoom

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

 Available Colloquium Friday, October 16, 2020 3:30 PM Physics Building, Room 204  Add to your calendar

## "Isolated Superfluid Liquid Helium Drops in a Magneto-Gravitational Trap"

Dr. Charles Brown II , University of California, Berkeley
[Host: Bellave Shivaram]
ABSTRACT:

The unique properties of superfluid 4He (low mechanical stiffness, zero viscosity, high structural and chemical purity and extremely low optical loss) may allow the direct pursuit of optomechanics with quantum mechanical oscillators. We have constructed an optomechanical system consisting entirely of a magnetically levitated drop of superfluid 4He in vacuum. Levitation removes a source of loss associated with physically clamped oscillators. and allows the drop to efficiently cool itself via evaporation. The drop’s optical whispering gallery modes (WGMs) and its surface vibrations couple to each other via the usual optomechanical interactions. We demonstrate the stable magnetic levitation of superfluid 4He drops in vacuum, and present measurements of the drops' evaporation rates, temperatures, optical modes and surface vibrations. We found optical modes with finesse ≈40 (limited by the drop's size). We found surface vibrations with decay rates 1 Hz (in rough agreement with theory). Lastly, we found that the drops reach a temperature T≈330 mK, and that a single drop can be trapped indefinitely.

VIDEO:
Colloquium
Friday, October 2, 2020
3:30 PM
online, Room via Zoom

## "Finding Needles in an Avalanche of Haystacks: The New Precision Timing Detector for CMS "

Chris Neu , University of Virginia - Department of Physics
[Host: Bob Jones]
ABSTRACT:

The full potential of the Large Hadron Collider will ultimately be realized through the running period that will take collider operations into the late 2030s. The so-called High Luminosity era of the LHC (HL-LHC), planned to begin in 2027, will see up to a 5-fold increase in the nominal brightness of the LHC beams, which will consequently allow experiments to collect a data set of proton-proton collisions approximately 20 times larger than what has been collected so far in high-energy LHC running. This significant increase in data sample will be a boon for the physics program of the LHC experiments, furthering searches for ultra-rare phenomena and refining precision measurements of known processes. At the CMS experiment, a suite of novel upgrades will be deployed that will enable the experiment to cope with the onslaught of collisions in the high luminosity environment and fully capitalize on the opportunities presented in the HL-LHC era. In this talk I will focus on the MIP Timing Detector (MTD), a device capable of measuring the time-of-arrival for minimum-ionizing particles (MIPs) produced within CMS with a resolution of 30 picoseconds. This entirely new detector system will be built in part at UVA before being shipped to CERN and integrated with the CMS experiment. I will describe the principle of operation of the MTD, the current status of the project and UVA's role in the construction of the device. I will also discuss the expected impact the MTD will have on several high-profile physics signatures that are prime targets in the HL-LHC era and, in particular, the power of using timing information in the reconstruction of exotic long-lived particle decays.

VIDEO:
Colloquium
Friday, September 25, 2020
3:30 PM
Online, Room via Zoom

## "Multiscale modeling of metal-insulator transition in correlated electron systems"

Gia-Wei Chern , University of Virginia - Department of Physics
[Host: Bob Jones]
ABSTRACT:

In this talk, I will present our recent efforts on dynamical simulations of correlated electron systems. I will first discuss new quantum molecular dynamics (QMD) methods based on advanced many-body techniques, such as Gutzwiller/slave-boson and dynamical mean-field theory, that are capable of modeling strong electron correlation phenomena. We apply our new QMD to simulate the correlation-induced Mott transition in a metallic liquid, and the nucleation-and-growth of Mott droplets in Hubbard-type models. I will also discuss the implementation of the ab initio Gutzwiller MD for simulating hydrogen liquids under high pressure. To overcome the obstacle of huge computational complexity in such large-scale simulations, I will discuss how simulation efficiency can be significantly improved with the aid of modern machine learning methods. In particular, deep-learning neural-network holds the potential of achieving large-scale quantum-accuracy simulation of correlated systems without the electrons.

VIDEO:
Colloquium
Friday, September 18, 2020
3:30 PM
Online, Room via Zoom

##### https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

 Unavailable Colloquium Friday, September 11, 2020 3:30 PM , Room unavailable  Add to your calendar

## "Programmable Quantum Simulation with Superconducting Qubits and Microwave Photons "

Professor Steven M. Girvin , Department of Physics and Yale Quantum Institute Yale University
[Host: Olivier Pfister and Israel Klich]
ABSTRACT:

‘Circuit QED’ is the quantum theory of superconducting qubits strongly interacting with microwave photons in electrical circuits. It is the leading solid-state architecture in the race to develop large-scale fault-tolerant quantum computers, and is the only technology that has demonstrated quantum error correction that actually extends the lifetime of quantum information.

In this talk, I will present an elementary introduction to the basic concepts underlying superconducting quantum processors. Their ability to control and make quantum non-demolition (QND) measurements of individual microwave photons is a powerful resource for quantum computation, communication and simulation.   I will illustrate these capabilities with recent experiments on a programmable quantum simulator that uses efficient boson sampling of microwave photons to predict the Franck-Condon vibrational spectra of various small tri-atomic molecules.  Finally, I will briefly explore possible future directions for simulation of quantum many-body problems involving interacting bosons.

VIDEO:
Colloquium
Friday, September 4, 2020
3:30 PM
online, Room via Zoom

#### Meeting ID: 997 4538 9785 Passcode: 540373

 Available Colloquium Friday, August 28, 2020 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, March 27, 2020 3:30 PM Physics Building, Room 204  Add to your calendar
 Reserved Colloquium Friday, March 20, 2020 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, March 13, 2020 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, March 6, 2020 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, February 28, 2020 3:30 PM Physics Building, Room 204  Add to your calendar

## "Integrated x(2) photonics"

Professor Hong Tang , Department of Electrical Engineering, Yale University
[Host: UVA Student Chapter of OSA/SPIE]
ABSTRACT:

The ability to generate and manipulate photons with high efficiency and coherence is of critical importance for both fundamental quantum optics studies and practical device applications. However mainstream integrated photonic platforms such as those based on silicon and silicon nitride lack the preferred cubic c(2) nonlinearity, which limits active photon control functionalities. In this talk, I will present integrated photonics based on aluminum nitride (AlN) and lithium niobite (LN), whose non-centrosymmetric crystal structures give rise to the strong second-order optical nonlinearity. Together with their low optical loss, the integrated AlN and LN photonics can provide enhanced c(2) photon-photon interactions to achieve high fidelity photon control, including on-chip parametric down-conversion, coherent light conversion, spectral-temporal shaping, and microwave-to-optical frequency conversions.

Colloquium
Monday, February 24, 2020
3:30 PM
Physics Building, Room 203

Special Colloquium

 "Wednesday's Special Colloquium will be shown" Colloquium Friday, February 21, 2020 3:30 PM Physics Building, Room 204  Add to your calendar

## "Deconfinement on Axion Domain Walls"

Mohamed Anber , Lewis & Clark College
[Host: Peter Arnold]
ABSTRACT:

The general lore, according to effective field theory, is that one ignores the high energy degrees of freedom when studying low energy phenomena. For example, we usually do not need to know quantum chromodynamics (QCD) (the strong nuclear force) in order to study fluid mechanics! However, the existence of 't Hooft anomalies (subtle phases in the partition function) may signal non-trivial intertwining between the high and low energy scales. This assertion can be seen in axion physics; axion is a hypothetical particle that may play important roles in solving a few puzzles in the Universe.  After a brief introduction to QCD and axions, I show how this intertwining takes place on axion domain walls (DW). To this end, I first discuss a new class of 't Hooft anomalies that was recently identified, and then use the anomalies to argue that quarks are deconfined (liberated) on axion DW. This newly discovered phenomenon implies that non-trivial interplay between different scales happens on the walls. Further, I confirm this picture by performing explicit calculations in a toy model, which is argued to be continuously connected to the full-fledged QCD.

Colloquium
Wednesday, February 19, 2020
3:30 PM
Physics Building, Room 204

Special Colloquium

 "Wednesday's Special Colloquium will be shown" Colloquium Friday, February 14, 2020 3:30 PM Physics Building, Room 204  Add to your calendar

## "New connections between Quantum Field Theory and String Theory"

Christoph Uhlemann , University of Michigan
[Host: Peter Arnold]
ABSTRACT:

Quantum field theory is a universal language in theoretical physics, which provides the foundation for the Standard Model of elementary particles, underlies the physics of the early universe, and describes a wealth of interesting phenomena in condensed matter. But despite its great successes, fully understanding this important framework is still very much a work in progress. Many insights, especially into theories with strong interactions, have been obtained using mathematical tools from string theory, and this has reshaped our understanding of what quantum field theory is. In this talk I will discuss new connections between quantum field theory and string theory that provide access to a remarkable class of theories that would not have been believed to exist based on conventional lore.

Colloquium
Wednesday, February 12, 2020
3:30 PM
Physics Building, Room 204

Special Colloquium

 Wednesday's Special Colloquium will be shown Colloquium Friday, February 7, 2020 3:30 PM Physics Building, Room 204  Add to your calendar

## "Neutrinos - Harbingers of New Physics"

Julian Heeck , University of California, Irvine
[Host: Peter Arnold]
ABSTRACT:

Neutrinos are the most elusive known elementary particles; they fly through all of us in vast numbers but are extremely difficult to detect. Immense progress has been made in analyzing their properties over the last decades, culminating in the surprising discovery of neutrino flavor oscillations. These neutrino oscillations imply that neutrinos have tiny but nonzero masses, which provides strong evidence for physics beyond the Standard Model of particle physics. With the increasing precision in neutrino measurements it has even become possible to use neutrinos as a tool to probe for further new physics, e.g. by studying how neutrinos scatter off electrons. In addition, neutrinos could prove uniquely helpful in the search for dark matter and provide complementary information to standard indirect detection signatures.

Colloquium
Wednesday, February 5, 2020
3:30 PM
Physics Building, Room 204

Special Colloquium

 Wednesday's Special Colloquium will be shown Colloquium Friday, January 31, 2020 3:30 PM Physics Building, Room 204  Add to your calendar

## "Generating New Physics from Known Particles: Baryogenesis and Dark Matter from Mesons"

Gilly Elor , University of Washington
[Host: Peter Arnold]
ABSTRACT:

I will address two of the most fundamental questions about our Universe -- "What is the Universe made of?” and "How did complex structures come to exist?”. These translate into understanding the origins of dark matter and a mechanism to generate the asymmetry of matter over anti-matter in the early Universe. I will put these problems in context and then present a novel, testable, solution to both mysteries in the same framework.  The key idea is to rely on Standard Model particles called Beauty (B) Mesons which decay into dark matter particles. This mechanism has multiple testable signals. Some experimental searches are already under development, the results of which could yield the first hints of how nature chose to address these profound questions.

Colloquium
Wednesday, January 29, 2020
3:30 PM
Physics Building, Room 204

Special Colloquium

## "What do we learn about gravity & nuclear physics from gravitational waves?"

Kent Yagi , University of Virginia - Department of Physics
[Host: Bob Jones]
ABSTRACT:

A hundred years after the prediction by Einstein, gravitational waves were directly detected for the first time in 2015 by LIGO, which marked the dawn of gravitational-wave astronomy. Gravitational waves are sourced by astrophysical compact objects, such as black holes and neutron stars. Due to their extremely large gravitational field and compactness, they offer us natural testbeds to probe strong-field gravity and dense matter physics. In this talk, I first give an overview of the current status of gravitational-wave observations. Next, I explain how well one can test General Relativity, constrain the equation of state of nuclear matter and measure nuclear parameters with gravitational waves. I also comment on how one can combine gravitational-wave information with the recent measurement of a neutron star radius by an X-ray payload NICER to further probe nuclear physics.

Colloquium
Friday, January 24, 2020
3:30 PM
Physics Building, Room 204

## "Quantum Open Systems and Field Theory"

Duff Neill , Los Alamos National Lab
[Host: Peter Arnold]
ABSTRACT:

When learning about the properties of a quantum mechanical system, for instance, the energy levels of its bound states, it is useful to think of the system as closed and isolated from any environment, though we know in any laboratory setting, all systems eventually will interact with an environment. However, we can often engineer such interactions to be weak, short-ranged, and controllable, so that the isolated approximation is a good one.

I will argue that in many physically relevant field theories, the long-time observables or states of the theory can only be defined in the context of a quantum open system, where we take into account the interactions between the system and the environment continually in the evolution of the system. This is because excitations of the field theory will inevitably create their own environment, that is, states we must trace over. Resumming these interactions with the self-created environment is necessary to give a convergent expansion for observables over all of phase-space.

Colloquium
Wednesday, January 22, 2020
3:30 PM
Physics Building, Room 204

Special Colloquium

 RESERVED Colloquium Friday, January 17, 2020 3:30 PM Physics Building, Room 204  Add to your calendar

## "The holographic view on transport in strongly interacting plasmas"

Saso Grozdanov , MIT
[Host: Peter Arnold]
ABSTRACT:

Microscopic quantum interactions between elementary particles control transport in macroscopic states of matter, such as in fluids and plasmas. In numerous states of interest, these microscopic interactions are strong, including in water, among electrons in graphene and in quark-gluon plasma — a state of nuclear matter that filled the early Universe and that is currently being recreated in particle colliders. While macroscopic theories describing the dynamics of such states, in particular, hydrodynamics (of fluids) and magnetohydrodynamics (of magnetized plasmas) have been partially understood, a full description of transport also requires a certain microscopic knowledge of its underlying quantum physics. After more than a century of striking advance in quantum theories, our theoretical understanding of these microscopic processes remains mostly limited to states with weak interactions. Recently, however, string theory also enabled explorations of strongly interacting states through the mathematical statement of holographic duality, which translates otherwise intractable problems into simpler analyses of black holes and gravitational waves.

In my talk, I will first discuss new aspects of the macroscopic theory of hydrodynamics, focusing on the properties of the infinite series of higher-order corrections to the infamous Navier-Stokes equations. By using a novel concept of generalized global symmetries, which can encode the fact that the number of magnetic flux lines in Nature is conserved, I will then describe the construction of a new, comprehensive theory of magnetohydrodynamics. This reformulation has led to a number of general theoretical and experimental predictions for transport in magnetized plasmas. I will then move on to discuss the microscopic physics responsible for transport in strongly interacting states. Beginning with an introduction of holographic duality, this section will summarize holographic insights into the problem of the “unreasonable effectiveness of hydrodynamics” for the description of quark-gluon plasma. Then, I will discuss how the descriptions of microscopic physics and transport transition between strongly and weakly interacting pictures. Finally, by utilizing the mathematical structure behind our new theory of magnetohydrodynamics, a holographic dual of magnetized plasmas will be presented along with the first analyses of strongly interacting magnetized transport.

Colloquium
Wednesday, January 15, 2020
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Exploring the Nucleon Sea"

Jen-Chieh Peng , University of Illinois at Urbana-Champaign
[Host: Simonetta Liuti]
ABSTRACT:

Direct experimental evidence for point-like constituents in the nucleons
was first found in the electron deep inelastic scattering (DIS) experiment.
The discovery of the valence and sea quark structures in the nucleons
inspired the formulation of Quantum Chromodynamics (QCD) as the gauge field
theory governing the strong interaction. A surprisingly large asymmetry
between the up and down sea quark distributions in the nucleon was observed
in DIS and the so-called Drell-Yan experiments. In this talk, I discuss the
current status of our knowledge on the flavor structure of the nucleon sea.
I will also discuss the progress in identifying the "intrinsic" sea
components in the nucleons. Future prospect for detecting some novel
sea-quark distributions will also be presented.

Colloquium
Friday, December 6, 2019
3:30 PM
Physics Building, Room 204

## "Multimessenger astronomy of compact binaries from the vantage point of computational gravity"

Prof. Vasileios Paschalidis , University of Arizona
[Host: Kent Yagi]
ABSTRACT:

We live in an exciting era where strong-field gravity has become a central pillar in the study of astrophysical sources.   For the first time in history the detection of gravitational waves and simultaneous electromagnetic signals (multimessenger astronomy) from the same source have the potential to solve some of the most long-standing problems in fundamental physics and astrophysics. Computational gravity plays an important role in the success of the multimessenger astronomy program. Using the vantage point of computational gravity, in this talk we will we focus on how observations of colliding neutron stars can teach us about the state of matter at densities greater than the nuclear density, and with a critical eye assess what we have learnt so far from the first observation of a binary neutron star (event GW170817). We will also discuss how multimessenger detection of collisions of binary black holes may inform us about their environments andthe nature of black holes.

Colloquium
Friday, November 15, 2019
3:30 PM
Physics Building, Room 203

Joint Colloquium with Physics and Astronomy/NRAO

## "Testing Einstein with numerical relativity: theories beyond general relativity, and the precision frontier"

Professor Leo Stein , University of Mississippi
[Host: Kent Yagi]
ABSTRACT:

Advanced LIGO and Virgo have already detected black holes crashing into each other at least ten times. With their upgrades we anticipate a rate of about 1 gravitational-wave detection per week. More signals and higher precision will take the dream of testing Einstein's theory of gravity, general relativity, and make it a reality. But would we know a correction to Einstein's theory if we saw it? How do we make predictions from theories beyond GR? And do current numerical relativity simulations have enough precision that we could be confident in any potential discrepancy between observations and predictions? I will discuss (i) how to perform simulations in beyond-GR theories of gravity, and (ii) how numerical relativity simulations need to improve to be ready for the precision frontier of gravitational wave astrophysics.

Colloquium
Friday, November 8, 2019
3:30 PM
Physics Building, Room 204

## "Studying the stars here on earth: Experimental investigations of the nuclear equation-of-state "

Sherry Yennello , Texas A&M University
[Host: Simonetta Liuti]
ABSTRACT:

Heavy-ion collisions can produce nuclear material over a range of densities and proton fractions to study the nuclear equation-of-state. These measurements are enabled by accelerating nuclei to – in some cases – GeV energies and detecting the fragments that are produced from the collisions.  The detectors are multi-detector arrays capable of measuring dozens of particles simultaneously from a single collision.  Data rates can range up to many hundreds of collisions per second. One can either explore the characteristics of the individual fragments that are produced, often extracting particle ratios or double ratios, or correlations between the fragments – in particular transverse collective flow.  From very low density to about three times normal nuclear density measurements have been made of the density dependence of the asymmetry energy.  I will present an overview of how these measurements have been made and the constraints they have set on the nuclear equation-of-state.

Colloquium
Friday, November 1, 2019
3:30 PM
Physics Building, Room 204

## "Phase space characterization of optical quantum states and quantum detectors"

Rajveer Nehra , University of Virginia - Physics
ABSTRACT:

We are in the midst of a second quantum revolution fueled by “quantumness” of physical systems and the sophisticated measurement devices or detectors to produce and characterize these exotic systems. Thus, characterization of quantum states and the detectors is a key task in optical quantum science and technology. The Wigner quasi-probability distribution function provides such a characterization. In this talk, I present our recent results on quantum state tomography of a single-photon Fock state using photon-number-resolving measurements using superconducting transition-edge sensor [1]. We directly probe the negativity of the Wigner function in our raw data without any inference or correction for decoherence, which is also an important indicator of the “quantum-only” nature of a physical system. For the second part of the talk, we discuss a method to characterize quantum detectors by experimentally identifying the Wigner functions of the detector positive-operator-value-measures (POVMs), a set of hermitian operators completely describing the detector [2]. The proposed scheme uses readily available thermal mixtures and probes the Wigner function point-by-point over the entire phase space from the detector’s outcome statistics. In order to make the reconstruction robust to the experimental noise, we use techniques from convex quadratic optimizations.

References
1. R. Nehra, A. Win, M. Eaton, R. Shahrokhshahi, N. Sridhar, T. Gerrits,A. Lita, S. W. Nam, and O. Pﬁster, “State-independent quantum state tomography by photon-number-resolving measurements,” Optica 6,1356–1360 (2019). 2. R. Nehra and K. Valson Jacob (2019), “Characterizing quantum detectors by Wigner functions,” [arXiv:1909.10628].

Colloquium
Friday, October 25, 2019
3:30 PM
Physics Building, Room 204

 Available Colloquium Friday, October 18, 2019 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, October 11, 2019 3:30 PM Physics Building, Room 204  Add to your calendar

## "Ferroelectric Polarons, Belgian Waffles, and Principles for âPerfectâ Semiconductors"

Professor Xiaoyang Zhu , Columbia University
[Host: Seunghun Lee]
ABSTRACT:

Lead halide perovskites have been demonstrated as high performance materials in solar cells and light-emitting devices. These materials are characterized by coherent band transport expected from crystalline semiconductors, but dielectric responses and phonon dynamics typical of liquids.  Here we explain the essential physics in this class of materials based on their dielectric functions and dynamic symmetry breaking on nano scales. We show that the dielectric function in the THz region may lead to dynamic and local ordering of polar nano domains by an extra electron or hole, resulting a quasiparticle which we call a ferroelectric large polaron, a concept similar to solvation in chemistry. Compared to a conventional large polaron, the collective nature of polarization in a ferroelectric large polaron may give rise to order(s)-of-magnitude larger reduction in the Coulomb potential. We show that the shape of a ferroelectric polaron resemble that of a Belgian waffle. Using two-dimensional coherent phonon spectroscopy, we directly probe the energetics and local phonon responses of the ferroelectric large polarons. We find that that electric field from a nascent e-h pair drives the local transition to a hidden ferroelectric order on picosecond time scale.  The ferroelectric or Belgian waffle polarons may explain the defect tolerance and low recombination rates of charge carriers in lead halide perovskites, as well as providing a design principle of the “perfect” semiconductor for optoelectronics.

Colloquium
Friday, October 4, 2019
3:30 PM
Physics Building, Room 204

 Available Colloquium Friday, September 27, 2019 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, September 20, 2019 3:30 PM Physics Building, Room 204  Add to your calendar

## "Quantum states, walks, tiles, and tensor networks"

Israel Klich , University of Virginia - Physics
[Host: Bob Jones]
ABSTRACT:

A major challenge of physics is the complexity of many-body systems. While true for classical systems, the difficulty is exasperated in quantum systems, due to entanglement between system components and thus the need to keep track of an exponentially large number of parameters. In particular, this complexity places a challenge to numerical methods such as quantum Monte Carlo and tensor networks. Here, exactly solvable models are of crucial importance:  we use these to test numerical procedures, to develop intuition, and as a starting point for approximations.

In this talk, I will explain our current understanding of a new solvable "walk" model, the area deformed Motzkin model. The model shows that entanglement may be more acute than previously thought, in particular, it features a novel quantum phase transition between a non-entangled phase and extensively entangled “rainbow” phase. Most remarkably, the model motivated the construction of a new tensor network, providing, after many years, the first example for an exact tensor network description of a critical system. Finally, I will remark on open problems, and on exciting connections to other fields such as the notion of holography in field theory, and a famous problem in non-equilibrium statistical mechanics.

Colloquium
Friday, September 13, 2019
3:30 PM
Physics Building, Room 204

## "Neutron stars droplets and the quarks within"

Professor Or Hen , MIT - Massachusetts Institute of Technology
[Host: Nilanga Liyanage]
ABSTRACT:

Neutron stars are one of the densest strongly-interacting many-body systems in our universe. A main challenge in describing the structure and dynamics of neutron stars steams from our limited understanding of the nuclear interaction at high-densities (i.e. short-distances) and its relation to the underlaying quark-gluon substructure of nuclei.

In this talk I will present new results from high-energy electron scattering experiments that probe the short-ranged part of the nuclear interaction via the hard breakup of Short-Range Correlations (SRC) nucleon pairs. As the latter reach densities comparable to those existing in the outer core of neutron stars, they represent ’neutron stars droplets’ who’s study can shed new light to the dynamical structure of neutron stars. Special emphasis will be given to the effect of SRCs to the behavior of protons in neutron-rich nuclear systems and how it can impact the cooling rates and equation of state of neutron stars.  Pursuing a more fundamental understanding of such interactions, I will present new measurements of the internal quark-gluon sub-structure of nucleons and show how its modification in the nuclear medium relates to SRC pairs and short-ranged nuclear interactions.

Given time I will also discuss the development of new effective theories for describing short-ranged correlations, the way in which they relate to experimental observables, and the emerging universality of short-distance and high-momentum physics in nuclear systems.

Colloquium
Friday, September 6, 2019
2:30 PM
Physics Building, Room 204

## "From interacting Majorana to universal fractional quasiparticles"

Jeffrey Teo , University of Virginia - Physics
[Host: Bob Jones]
ABSTRACT:

Ising anyons, Majorana fermions (MF) and zero energy Majorana bound states have promising prospects in topological quantum computing (TQC) because of their ability to store quantum states non-locally in space and insensitivity to local decoherence. Unfortunately, these objects are not powerful enough to assemble a TQC that can perform universal operations using topological braiding operations alone. On the other hand, there are anyonic quasiparticles, like the Fibonacci anyon in a Read-Rezayi quantum Hall state, that are universal in the braiding-based TQC sense. However, these are quantum dynamical excitations, which can be challenging to spatially manipulate and susceptible to temperature fluctuations in a thermodynamic system. We propose and define a new notion of universal fractional quasiparticles, which are semi-classical static topological defects, supported by many-body interacting MFs in a superconducting spin-orbit coupled topological electronic system.

VIDEO:
Colloquium
Friday, August 30, 2019
3:30 PM
Physics Building, Room 204

## "From Multimessenger Astronomy to Neutrons and Protons"

Andrew Steiner , University of Tennessee
[Host: Kent Yagi]
ABSTRACT:

Of course, multimessenger astronomy promises to revolutionize

astronomy and our understanding of nucleosynthesis. My

research shows that it goes further: astronomical observations

(via both photons and gravitational waves) provides a unique

laboratory to deepen our understanding of QCD and the

nucleon-nucleon interaction. Most current work is focused

on the equation of state. While the equation of state is

indeed important, in this talk, I show how we can

go beyond energy density and pressure. I present the first

large-scale Bayesian inference of neutron star observations

and nuclear structure data to obtain novel results on the

composition of dense matter and the nature of nucleonic

superfluidity.

Colloquium
Friday, April 26, 2019
3:30 PM
Physics Building, Room 204

Joint Colloquium with Physics and Astronomy/NRAO

## "Emergence of Mass in the Standard Model"

Dr. Craig D. Roberts , Argonne National Laboratory
[Host: Nilanga Liyanage]
ABSTRACT:

Quantum Chromodynamics (QCD), the nuclear physics part of the Standard Model, is the first theory to demand that science fully resolve the conflicts generated by joining relativity and quantum mechanics.  Hence in attempting to match QCD with Nature, it is necessary to confront the innumerable complexities of strong, nonlinear dynamics in relativistic quantum field theory.  The peculiarities of QCD ensure that it is also the only known fundamental theory with the capacity to sustain massless elementary degrees-of-freedom, gluons (gauge bosons) and quarks (matter fields); and yet gluons and quarks are predicted to acquire mass dynamically so that the only massless systems in QCD are its composite Nambu-Goldstone bosons.  All other everyday bound states possess nuclear-size masses, far in excess of anything that can directly be tied to the Higgs boson.  These points highlight the most important unsolved questions within the Standard Model, namely: what is the source of the mass for the vast bulk of visible matter in the Universe and how is this mass distributed within hadrons?  This presentation will provide a contemporary sketch of the strong-QCD landscape and insights that may help in answering these questions.

Colloquium
Friday, April 19, 2019
3:30 PM
Physics Building, Room 204

## "Computing Images from Weak Optical Signals"

Dr. Vivek Goyal , Boston University
[Host: MIller Eaton]
ABSTRACT:

In conventional imaging systems, the results are poor unless there is a physical mechanism for producing a sharp image with high signal-to-noise ratio.  In this talk, I will present two settings where computational methods enable imaging from very weak signals:  range imaging and non-line-of-sight (NLOS) imaging.

Lidar systems use single-photon detectors to enable long-range reflectivity and depth imaging.  By exploiting an inhomogeneous Poisson process observation model and the typical structure of natural scenes, first-photon imaging demonstrates the possibility of accurate lidar with only 1 detected photon per pixel, where half of the detections are due to (uninformative) ambient light.  I will explain the simple ideas behind first-photon imaging and lightly touch upon related subsequent works that mitigate the limitations of detector arrays, withstand 25-times more ambient light, allow for unknown ambient light levels, and capture multiple depths per pixel.

NLOS imaging has been an active research area for almost a decade, and remarkable results have been achieved with pulsed lasers and single-photon detectors.  Our work shows that NLOS imaging is possible using only an ordinary digital camera.  When light reaches a matte wall, it is scattered in all directions.  Thus, to use a matte wall as if it were a mirror requires some mechanism for regaining the one-to-one spatial correspondences lost from the scattering.  Our method is based on the separation of light paths created by occlusions and results in relatively simple computational algorithms.

Related paper DOIs:
10.1126/science.1246775
10.1109/TSP.2015.2453093
10.1109/LSP.2015.2475274
10.1364/OE.24.001873
10.1038/ncomms12046
10.1109/TSP.2017.2706028
10.1038/s41586-018-0868-6

Colloquium
Friday, April 12, 2019
3:30 PM
Physics Building, Room 204

 Available Colloquium Friday, April 5, 2019 3:30 PM Physics Building, Room 204  Add to your calendar

## "Interfaces in oxide quantum heterostructures"

Dr. Ho Nyung Lee , Oak Ridge National Laboratory
[Host: Seunghun Lee]
ABSTRACT:

Complex oxides are known to possess the full spectrum of fascinating properties, including magnetism, colossal magneto-resistance, superconductivity, ferroelectricity, pyroelectricity, piezoelectricity, multiferroicity, ionic conductivity, and more. This breadth of remarkable properties is the consequence of strong coupling between charge, spin, orbital, and lattice symmetry. Spurred by recent advances in the synthesis of such artificial materials at the atomic scale, the physics of oxide heterostructures containing atomically smooth layers of such correlated electron materials with abrupt interfaces is a rapidly growing area. Thus, we have established a growth technique to control complex oxides at the level of unit cell thickness by pulsed laser epitaxy. The atomic-scale growth control enables to assemble the building blocks to a functional system in a programmable manner, yielding many intriguing physical properties that cannot be found in bulk counterparts. In this talk, examples of artificially designed, functional oxide heterostructures will be presented, highlighting the importance of heterostructuring, interfacing, and straining. The main topics include (1) charge transfer induced interfacial magnetism and topologically non-trivial spin textures in SrIrO3-based heterostructures and (2) lattice and chemical potential control of oxygen stability and associated electronic and magnetic properties in nickelate-and cobaltite-based heterostructures.

This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

Colloquium
Friday, March 29, 2019
3:30 PM
Physics Building, Room 204

## "A Mathematical Journey Thru SUSY, Error-Correcting Codes, Evolution, and a Sustainable Reality "

Jim Gates, Ph.D. , Brown University
[Host: Diana Vaman]
ABSTRACT:

This presentation describes an arc in mathematical/theoretical physics traversing concepts from equations, graphs, error-correction, and pointing toward an evolution-like process acting on the  mathematical laws that sustain reality.

Colloquium
Friday, March 22, 2019
3:30 PM
Physics Building, Room 204

## "Available"

Colloquium
Friday, March 8, 2019
3:30 PM
Physics Building, Room 204

## "Kelvin-Froude wake patterns of a traveling pressure disturbance"

Genya Kolomeisky , University of Virginia - Physics
[Host: Israel Klich]
ABSTRACT:

Water wave patterns behind ships fuel human curiosity because they are both beautiful and easily observed.  These patterns called wakes were famously described in 1887 by Lord Kelvin.  According to Kelvin, the feather-like appearance of the wake is universal and the entire wake is confined within a 39 degree angle.  While such wakes have been observed, deviations from Kelvin’s predictions have also been reported.  In this talk summarizing my work with UVA alumnus Jonathan Colen I will present a quantitative reasoning based on classical surface water wave theory that explains why some wakes are similar to Kelvin’s prediction, and why others are less so.  The central result is a classification of wake patterns which all can be understood in terms of the problem originally treated by Kelvin.

Colloquium
Friday, March 1, 2019
3:30 PM
Physics Building, Room 204

 Available Colloquium Thursday, February 28, 2019 3:30 PM Physics Building, Room 204  Add to your calendar
 Reserved [Host: Diana Vaman] Colloquium Friday, February 22, 2019 3:30 PM Physics Building, Room 204  Add to your calendar

## "Gravitational waves and fundamental properties of matter and spacetime"

David Nichols , University of Amsterdam
[Host: Diana Vaman]
ABSTRACT:

Gravitational waves from the mergers of ten binary black holes and one binary neutron star were detected in the first two observing runs by the Advanced LIGO and Virgo detectors. In this talk, I will discuss the eleven gravitational-wave detections and the electromagnetic observations that accompanied the neutron-star merger. These detections confirmed many of the predictions of general relativity, and they initiated the observational study of strongly curved, dynamical spacetimes and their highly luminous gravitational waves. One aspect of these high gravitational-wave luminosities that LIGO and Virgo will be able to measure is the gravitational-wave memory effect: a lasting change in the gravitational-wave strain produced by energy radiated in gravitational waves. I will describe how this effect is related to symmetries and conserved quantities of spacetime, how the memory effect can be measured with LIGO and Virgo, and how new types of memory effects have been recently predicted. I will conclude by discussing the plans for the next generation of gravitational-wave detectors after LIGO and Virgo and the scientific capabilities of these new detectors. These facilities could detect millions of black-hole and neutron-star mergers per year, and they can provide insights on a range of topics from the population of short gamma-ray bursts to the presence of dark matter around black holes.

Colloquium
Wednesday, February 20, 2019
3:30 PM
Physics Building, Room 204

Special Colloquium

 Reserved [Host: Diana Vaman] Colloquium Friday, February 15, 2019 3:30 PM Physics Building, Room 204  Add to your calendar

## "Frontiers in Multi-Messenger Astrophysics at the interface of gravitational wave astrophysics, large scale astronomical surveys and data science "

Eliu Huerta , University of Illinois at Urbana-Champaign
[Host: Diana Vaman]
ABSTRACT:

The next decade promises fundamental new scientific insights and discoveries from Multi-Messenger Astrophysics, enabled through the convergence of large scale astronomical surveys, gravitational wave astrophysics, deep learning and large scale computing. In this talk I describe a Multi-Messenger Astrophysics science program, and highlight recent accomplishments at the interface of gravitational wave astrophysics, numerical relativity and deep learning. I discuss the convergence of this program with large scale astronomical surveys in the context of gravitational wave cosmology. Future research and development activities are discussed, including a vision to leverage data science initiatives at the University of Virginia to spearhead, maximize and accelerate discovery in the nascent field of Multi-Messenger Astrophysics.

Colloquium
Wednesday, February 13, 2019
3:30 PM
Physics Building, Room 204

Special Colloquium

 Reserved [Host: Diana Vaman] Colloquium Friday, February 8, 2019 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Thursday, February 7, 2019 3:30 PM Physics Building, Room 204  Add to your calendar

## "Black Hole Bridges"

Robert Penna , Columbia University
[Host: Diana Vaman]
ABSTRACT:

Black holes are bridges between astrophysics and fundamental physics.  I will describe three examples of this theme.  First, I will explain how contemporary theoretical ideas deriving from the holographic principle have proven useful for interpreting numerical simulations of electromagnetic outflows from spinning black holes.  These models are currently being tested against X-ray and radio observations of galactic black holes.  Second, I will describe a correspondence between black holes and lower dimensional fluids and discuss the possibility of probing this correspondence with gravitational wave memory experiments.  Finally, I will describe how gravitational wave observations of black hole tidal interactions might be used to find new symmetries acting on the event horizon.

Colloquium
Wednesday, February 6, 2019
3:30 PM
Physics Building, Room 204

Special Colloquium

 Reserved [Host: Diana Vaman] Colloquium Friday, February 1, 2019 3:30 PM Physics Building, Room 204  Add to your calendar

## "Testing Gravity with Cosmology and Astrophysics"

Jeremy Sakstein , University of Pennsylvania
[Host: Diana Vaman]
ABSTRACT:

We are entering a golden age of cosmology and astrophysics. In the coming decade we will have cosmological data for over a billion galaxies, a census of objects in the Milky Way, and a network of gravitational detectors spanning the globe that will detect thousands of events per year. This presents us with the unprecedented opportunity to learn how gravity behaves at the largest distances, and in the most extreme environments. In this talk I will describe how we can use current and upcoming data to understand the unexplained mysteries of the Universe, such as why the expansion of the Universe accelerating (dark energy). I will also discuss how to connect physics in these disparate regimes and how to test cosmology on small scales. To maximize the discovery potential of the data requires us to construct robust theoretical models, identify novel probes, and connect theory with observation, and I will describe projects where I have attempted to accomplish this. I will conclude the talk by discussing how this interdisciplinary effort will continue into the next decade and beyond.

Colloquium
Wednesday, January 30, 2019
3:30 PM
Physics Building, Room 204

Special Colloquium

 Available Colloquium Friday, January 25, 2019 3:30 PM Physics Building, Room 204  Add to your calendar

## "Probing Massive and Supermassive Black Holes with Gravitational Waves"

Sarah Vigeland , University of Wisconsin Milwaukee
[Host: Diana Vaman]
ABSTRACT:

Observations have shown that nearly all galaxies harbor massive or supermassive black holes at their centers. Gravitational wave (GW) observations of these black holes will shed light on their growth and evolution, and the merger histories of galaxies. Massive and supermassive black holes are also ideal laboratories for studying strong-field gravity. Pulsar timing arrays (PTAs) are sensitive to GWs with frequencies ~1-100 nHz, and can detect GWs emitted by supermassive black hole binaries, which form when two galaxies merge. The Laser Interferometer Space Antenna (LISA) is a planned space-based GW detector that will be sensitive to GWs ~1-100 mHz, and it will see a variety of sources, including merging massive black hole binaries and extreme mass-ratio inspires (EMRIs), which consist of a small compact object falling into a massive black hole. I will discuss source modeling and detection techniques for LISA and PTAs, as well as present limits on nanohertz GWs from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration.

Colloquium
Wednesday, January 23, 2019
3:30 PM
Physics Building, Room 204

Special Colloquium

## "The Electron Ion Collider Science "

Markus Diefenthaler , Jefferson Lab
[Host: Simonetta Liuti]
ABSTRACT:

Quantum Chromodynamics (QCD), the theory of the strong interaction, is a cornerstone of the Standard Model of modern physics. It explains all nuclear matter as bound states of point-like fermions, known as quarks, and gauge bosons, known as gluons. The gluons bind not only quarks but also interact with themselves. Unlike with the more familiar atomic and molecular matter, the interactions and structures are inextricably mixed up, and the observed properties of nucleons and nuclei, such as mass and spin, emerge out of this complex system. To precisely image the quarks and gluons and their interactions and to explore the new QCD frontier of strong color fields in nuclei, the Nuclear Physics community proposes an US-based Electron Ion collider (EIC) with high-energy and high-luminosity, capable of a versatile range of beam energies, polarizations, and ion species. The community is convinced that the EIC is the right tool to understand how matter at its most fundamental level is made.

Colloquium
Friday, January 18, 2019
3:30 PM
Physics Building, Room 204

## "Quantum Engineering: A Transdisciplinary Vision"

Prem Kumar , Northwestern University
[Host: Bob Jones]
ABSTRACT:

A global quantum revolution is currently underway based on the recognition that the subtler aspects of quantum physics known as superposition (wave-like aspect), measurement (particle-like aspect), and entanglement (inseparable link between the two aspects) are far from being merely intriguing curiosities, but can be transitioned into valuable, real-world technologies with performances that can far exceed those obtainable with classical technologies. The recent demonstration by the Chinese scientists of using a low-earth-orbit satellite to distribute entangled photons to two ground stations that are over a thousand kilometers apart is a stunning technological achievement—direct entanglement distribution over the best available fiber links is limited to a few hundred kilometers—and a harbinger of future possibilities for globally secure communications guaranteed by the power of quantum physics.

Harnessing the advantages enabled by superposition, measurement, and entanglement (SME)—the three pillars of quantum physics—for any given application is what is termed quantum engineering in general. In many instances, however, the details of the underlying science (high-temperature superconductivity, photosynthesis, avian navigation, are some examples) is still not fully understood, let alone how to turn the partially understood science into a potentially useful technology. Nevertheless, it has become clear in the last few decades that quantum engineering will require a truly concerted effort that will need to transcend the traditional disciplinary silos in order to create and sustain new breeds of science and technology communities that will be equally versed in quantum physics as they would be in their chosen area of technology. In this talk, I will present my vision for unleashing the potential of quantum engineering, taking some examples from ongoing and proposed research.

Colloquium
Thursday, January 17, 2019
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Frontiers of Multi-Messenger Black-Hole Physics"

Stephen Taylor , California Institute of Technology
[Host: Diana Vaman ]
ABSTRACT:

The bounty of gravitational-wave observations from LIGO and Virgo has opened up a new window onto the warped Universe, as well as a pathway to addressing many of the contemporary challenges of fundamental physics. I will discuss how catalogs of stellar-mass compact object mergers can probe the unknown physical processes of binary stellar evolution, and how these systems can be harnessed as standard distance markers (calibrated entirely by fundamental physics) to map the expansion history of the cosmos. The next gravitational-wave frontier will be opened within 3-6 years by pulsar-timing arrays, which have unique access to black-holes at the billion to ten-billion solar mass scale. The accretionary dynamics of supermassive black-hole binaries should yield several tell-tale signatures observable in upcoming synoptic time-domain surveys, as well as gravitational-wave signatures measurable by pulsar timing. Additionally, pulsar-timing arrays are currently placing compelling constraints on modified gravity theories, cosmic strings, and ultralight scalar-field dark matter. I will review my work on these challenges, as well as in the exciting broader arena of gravitational-wave astrophysics, and describe my vision for the next decade of discovery.

Colloquium
Wednesday, January 16, 2019
3:30 PM
Physics Building, Room 204

Special Colloquium

## " Using Topology to Solve Strongly Coupled Quantum Field Theories"

Zohar Komargodski , Stony Brook University
[Host: Marija Vucelja]
ABSTRACT:

I will begin by describing an interacting model in Quantum Mechanics where exact results about the ground state can be established by using tools from topology. I will then argue that such tools are also useful for tackling interesting problems in Quantum Field Theory. In particular, I will review Yang-Mills theory and argue that using topology one can make several predictions about its possible phases. We will then also extend the considerations to Quantum Chromodynamics and discuss possible connections with particle physics phenomenology and with condensed matter physics.

Colloquium
Friday, December 7, 2018
3:30 PM
Physics Building, Room 204

## "A new approach to search for neutron-antineutron oscillations, and a couple of other phenomena based on neutron reflection from surface: gravitational and whispering-gallery quantum states of neutrons"

Valery Nesvizhevsky , Institut Laue Langevin, France
[Host: Stefan Baessler]
ABSTRACT:

“An observation of neutron-antineutron oscillations (n-n ̅), which violate both B and B — L conservation, would constitute a scientific discovery of fundamental importance to physics and cosmology. A stringent upper bound on its transition rate would make an important contribution to our understanding of the baryon asymmetry of the universe by eliminating the post-sphaleron baryogenesis scenario in the light quark sector. We show that one can design an experiment using slow neutrons that in principle can reach the required sensitivity of 1010 s in the oscillation time, an improvement of 104 in the oscillation probability relative to the existing limit for free neutrons. This can be achieved by allowing both the neutron and antineutron components of the developing superposition state to coherently reflect from mirrors. We present a quantitative analysis of this scenario and show that, for sufficiently small transverse momenta of n/n ̅ and for certain choices of nuclei for the n/n ̅ guide material, the relative phase shift of the n and n ̅ components upon reflection and the n ̅ annihilation rate can be small. While the reflection of n ̅ from surface looks exotic and counterintuitive and seems to contradict to the common sense, in fact it is fully analogous to the reflection of n from surface. The later phenomenon is well known and used in neutron research from its first years. We illustrate it with two selected example of gravitational and whispering-gallery quantum states of neutrons.”

[V.V. Nesvizhevsky, A.Yu. Voronin, Surprising Quantum Bounces, Imperial College Press, London, 2015]

Colloquium
Friday, November 30, 2018
3:30 PM
Physics Building, Room 204

## "Energy-efficient neuromorphic computing with magnetic tunnel junctions"

Mark Stiles , NIST
[Host: Joe Poon & Avik Ghosh]
ABSTRACT:

Human brains can solve many problems with orders of magnitude more energy efficiency than traditional computers.  As the importance of such problems, like image, voice, and video recognition, increases, so does the drive to develop computers that approach the energy efficiency of the brain.  Magnetic devices, especially tunnel junctions, have several properties that make them attractive for such applications.  Their conductance depends on the state of the ferromagnets making it easy to read information that is stored in their magnetic state.  In addition, current can manipulate the magnetic state.  Based on this electrical control of the magnetic state, magnetic tunnel junctions are actively being developed for integration into CMOS integrated circuits to provide non-volatile memory.  This development makes it feasible to consider other geometries that have different properties.  I describe two of the computing primitives that have been constructed based on the different functionalities of magnetic tunnel junctions.  The first of these uses tunnel junctions in their superparamagnetic state as the basis for a population coding scheme.  The second uses them as non-linear oscillators in the first nanoscale “reservoir” for reservoir computing.

Colloquium
Friday, November 16, 2018
3:30 PM
Physics Building, Room 204

## "Thermal relaxations, the Mpemba effect, and adaptation of bacteria "

Marija Vucelja , UVA-Physics
[Host: Bob Jones]
ABSTRACT:

Most of my talk will be about anomalous thermal relaxations, such as the Mpemba effect. Towards the end of my talk, I will also highlight a few topics in population dynamics that I have been working on.

The Mpemba effect is a phenomenon when "hot can cool faster than cold" - a “shortcut” in relaxation to thermal equilibrium. It occurs when a physical system initially prepared at a hot temperature, cools down faster than an identical system prepared at a colder temperature. The effect was discovered as a peculiarity of water. Despite following observations in granular gasses, magnetic alloys, and spin glasses, the effect is still most often referred to as an “oddity” of water, although it is widespread and general.  I will describe how to define a Mpemba effect for an arbitrary physical system, and show how to quantify and estimate the probability of the Mpemba effect on a few examples.

In the remaining time, I will briefly talk about the adaptation of bacterial populations and the immune system of bacteria with CRISPR.  Besides being the biology's newest buzzword and favorite gene editing tool, CRISPR is also a mechanism that allows bacteria to defend adaptively against phages and other invading genomic material. From the standpoint of physics and biology, the coevolution of bacteria and phages yields fascinating open questions.

Colloquium
Friday, November 9, 2018
3:30 PM
Physics Building, Room 204

 Available Colloquium Friday, November 2, 2018 3:30 PM Physics Building, Room 204  Add to your calendar

## ""Building a Quantum Computer Using Silicon Quantum Dots""

Susan Coppersmith , University of Wisconsin - Madison
[Host: Despina Louca]
ABSTRACT:

The steady increase in computational power of information processors over the past half-century has led to smart phones and the internet, changing commerce and our social lives.  Up to now, the primary way that computational power has increased is that the electronic components have been made smaller and smaller, but within the next decade feature sizes are expected to reach the fundamental limits imposed by the size of atoms.  However, it is possible that further huge increases in computational power could be achieved by building quantum computers, which exploit in new ways of the laws of quantum mechanics that govern the physical world.  This talk will discuss the challenges involved in building a large-scale quantum computer as well as progress that we have made in developing a quantum computer using silicon quantum dots.  Prospects for further development will also be discussed.

Colloquium
Friday, October 26, 2018
3:30 PM
Physics Building, Room 204

## "Available"

Colloquium
Friday, October 19, 2018
3:30 PM
Physics Building, Room 204

 Available Colloquium Friday, October 12, 2018 3:30 PM Physics Building, Room 204  Add to your calendar

## "Unveiling the Normal State of Cuprate High-Temperature Superconductors: Hidden Order of Cooper Pairs"

Dragana Popovic , Florida State University
[Host: Despina Louca]
ABSTRACT:

Many unusual properties of strongly correlated materials have been attributed to the proximity of quantum phase transitions (QPTs), where different types of orders compete and coexist, and may even give rise to novel phases.  In two-dimensional (2D) systems, the nature of the magnetic-field-tuned QPT from a superconducting to a normal state has been widely studied, but it remains an open question.  Underdoped copper-oxide high-temperature superconductors are effectively 2D materials and thus present a promising new platform for exploring this long-standing problem.  Although in cuprates the normal state is commonly probed by applying a perpendicular magnetic field (H) to suppress superconductivity, the identification and understanding of the H-induced normal state has been a challenge because of the complex interplay of disorder, temperature and quantum fluctuations, and the near-universal existence of charge-density-wave correlations.

This talk will describe recent experimental advances in identifying and characterizing a full sequence of ground states as a function of H in underdoped cuprates.  In both the absence and the presence of charge order, the results demonstrate the key role of disorder in the H-tuned suppression of 2D superconductivity, giving rise to an intermediate regime with large quantum phase fluctuations, in contrast to the conventional scenario.  Most strikingly, the interplay of the “striped” charge order with high-temperature superconductivity leads to the emergence of an unanticipated, insulatinglike ground state with strong superconducting phase fluctuations, suggesting an unprecedented freezing (i.e. “the hidden order”) of Cooper pairs.  Possible scenarios will be discussed, including the implications of the results for understanding the physics of the cuprate pseudogap regime, as well as other 2D superconductors.

Colloquium
Friday, October 5, 2018
3:30 PM
Physics Building, Room 204

## "Charge density wave phase transitions in transition metal dichalcogenides"

Utpal Chatterjee , University of Virginia - Department of Physics
[Host: Bob Jones]
ABSTRACT:

Layered transition-metal dichalcogenides (TMDs) are well known for their rich phase diagrams, which
encompass diverse quantum states including metals, semiconductors, Mott insulators, superconductors, and
charge density waves (CDWs). For instance, 2H-NbSe2 and 2H-TaS2 are canonical incommensurate CDW
systems, while 1T-TiSe2 harbors a commensurate CDW order. There is a coexistence/competition of CDW
and superconductivity in 2H-NbSe2 and 2H-TaS2, though this is not the case for pristine 1T-TiSe2. A subtle
interplay of CDW and superconducting orders, however, appears in each of these materials via chemical
intercalation or under pressure. Such a competition between or coexistence of proximate broken-symmetry
phases resembles many aspects of the phase diagram of cuprate high temperature superconductors
(HTSCs)—particularly, in the underdoped regime where the enigmatic pseudogap phase exists. The origin
of the CDW order in these compounds is an intriguing puzzle despite decades of research. We will present
our experimental data, which combine Angle Resolved Photoemission Spectroscopy, Scanning Tunneling
Spectroscopy, scattering and transport measurements, to provide new insights into the relative importance
of lattice and Coulomb effects in the CDW transitions of these compounds. These studies will also highlight
the distinctive impacts of disorder and doping in commensurate and incommensurate CDW systems.
Finally, comparing spectroscopic features of the CDW state of the TMDs with those of the normal state
underdoped HTSCs, we will discuss whether a CDW order can possibly be the origin of the pseudogap
phase in the cuprates.

Colloquium
Thursday, October 4, 2018
3:30 PM
Physics Building, Room 204

## "FeynmanÊ¼s Footprints: Quantum Field Theory in Nuclear and Particle Physics"

Roxanne Springer , Duke University
[Host: Simonetta Liuti]
ABSTRACT:

2018 is the 100th Anniversary of the birth of Richard Feynman.
His discoveries and new formalisms, and the way he thought about
solving problems, transformed the way we think
about physics. I will talk about examples of how these impacted present results
in nuclear and particle physics.

I will also expand upon what might be called Feynmanʼs Scientific Method,
and how by following that method we can become better scientists ourselves
and nurture the next generation of scientists.

Colloquium
Friday, September 28, 2018
3:30 PM
Physics Building, Room 204

## "Emergent Gravity"

Diana Vaman , University of Virginia - Physics
[Host: Bob Jones]
ABSTRACT:

Is gravity a fundamental force? I will discuss a few scenarios in which gravity emerges from the dynamics of some underlying field theory. In holography (or AdS/CFT correspondence), Einstein's equations for the bulk gravity dual are linked to entanglement in the boundary field theory. In another example, the graviton emerges as a composite spin two massless particle in a scalar field theory.

SLIDESHOW:
Colloquium
Monday, September 24, 2018
3:30 PM
Physics Building, Room 203

Slideshow (PDF)

 Available Colloquium Friday, September 21, 2018 3:30 PM Physics Building, Room 204  Add to your calendar

## "Available"

Colloquium
Friday, September 14, 2018
3:30 PM
Physics Building, Room 204

## "Searching for Supersymmetry with the ATLAS experiment"

Evelyn Thomson , University of Pennsylvania
[Host: Chris Neu]
ABSTRACT:

The ATLAS experiment is searching new territory for evidence of new particles produced in proton collisions at the highest energies.  Questioning assumptions is important in these searches. I will compare selected results from searches for supersymmetry with and without the assumption of R-Parity, a quantum number derived from the spin and type of particle.  I will also present some of the detector-related challenges associated with measuring charged particle momenta, including the planned upgrade of the detector to cope with up to 200 proton collisions every 25 nanoseconds.

Colloquium
Friday, September 7, 2018
3:30 PM
Physics Building, Room 204

 Please See Condensed Matter Seminar Schedule Colloquium Friday, August 31, 2018 3:30 PM Physics Building, Room 204  Add to your calendar

## "The Brave nu World"

Andre Luiz De Gouvea , Northwestern University
[Host: P. Q. Hung]
ABSTRACT:

I will review the current theoretical and phenomenological status of neutrino physics. In more detail, I will discuss our current understanding of neutrino properties, open questions, some new physics ideas behind nonzero neutrino masses, and the challenges of piecing together the neutrino mass puzzle. I will also comment on the new physics reach of the current and the next generation of neutrino oscillation experiments.

SLIDESHOW:
Colloquium
Friday, April 27, 2018
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "High-Q Optical Micro-cavities: Towards Integrated Optical Time Standards and Frequency Synthesizers"

Kerry Vahala , Caltech
[Host: OSA/SPIE Student Chapter]
ABSTRACT:

Communication systems leverage the respective strengths of optics and electronics to convey high-bandwidth signals over great distances.  These systems were enabled by a revolution in low-optical-loss dielectric fiber, complex integrated circuits as well as devices that link together the optical and electrical worlds.  Today, another revolution is leveraging the advantages of optics and electronics in new ways.  At its center is the laser frequency comb which provides a coherent link between these two worlds. Significantly, because the link is also bidirectional, performance attributes previously unique to electronics and optics can be shared. The end result has been transformative for time keeping, frequency metrology, precision spectroscopy, microwave-generation, ranging and other technologies. Even more recently, low-optical-loss dielectrics, now in the form of high-Q optical resonators, are enabling the miniaturization of frequency combs. These new microcombs’ can be integrated with electronics and other optical components to potentially create systems on-a-chip.  I will briefly overview the history and elements of frequency combs as well as the physics of the new microcombs. Application of the microcombs for spectroscopy and LIDAR will be discussed.  Finally, efforts underway to develop integrated optical clocks and integrated optical frequency synthesizers using the microcomb element are described.

Colloquium
Thursday, April 26, 2018
3:30 PM
Physics Building, Room 204

## "Teaching physics as it is done: A plea for qualitative methods "

[Host: Olivier Pfister]
ABSTRACT:

It is customary for young physicists, when entering their professional career, to be astonished by the huge difference between physics as it is done and physics as it is taught. The purpose is to show that teaching of physics as it is done is indeed possible and should be encouraged, despite the undeniable existence of didactical, epistemological and institutional obstacles.

Colloquium
Friday, April 20, 2018
3:30 PM
Physics Building, Room 204

## "Using Dynamic Interferometry to Measure Optics of Next Generation Telescopes"

James Wyant , University of Arizona
[Host: OSA/SPIE Student Chapter]
ABSTRACT:

There are currently several large telescope projects. One new telescope is the James Webb Space Telescope (JWST) which is planned to be launched into space on an Ariane 5 rocket from French Guiana in Spring 2019. It is expected that JWST will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System. The primary mirror will consist of 18 mirror segments made of beryllium coated with gold to give a total aperture diameter of 6.5 m. It is critical that the 18 mirror segments are properly phased so they perform as a single 6.5 m diameter mirror. JWST's backplane is the large structure that holds and supports the big hexagonal mirrors of the telescope. The backplane has an important job as it must carry not only the 6.5 m diameter primary mirror plus other telescope optics, but also the entire module of scientific instruments. The mechanical stability and thermal characteristics of the graphite composite backplane are extremely important for optimum performance of the telescope. JWST has many challenging optical testing requirements including a) Primary mirror figure testing, b) Back structure measurement, c) Segment phasing, d) Thermal and mechanical strain, and e) Vibrational dynamics.

Another telescope currently being constructed is the Giant Magellan Telescope (GMT), a large ground-based telescope consisting of seven 8.5 m diameter mirrors that will be built on a peak in the Andes Mountains near several existing telescope facilities at Las Campanas, Chile at an altitude of over 2,550 meters. The seven 8.4 m diameter mirror segments will be phased to give a telescope having the resolving power of a telescope 24.5 meters in diameter. GMT is expected to be operational for many decades, enabling breakthrough science ranging from studies of the first stars and galaxies in the universe to the exploration of extrasolar alien worlds. The GMT is poised to answer some of humanity’s biggest questions about the nature of exoplanets and whether we are alone in the universe, about the beginning of the universe to understand the formation and evolution of the galaxies, about the origin of the chemical elements, and how black holes grow. Like the JWST, the GMT has many challenging testing requirements.

During this talk we will describe the JWST and the GMT and the dynamic interferometry techniques that have been developed to measure high quality large telescope optics and the surface vibration and stability characteristics of the supporting structure required for high-quality performance large telescopes.

Colloquium
Friday, April 13, 2018
3:30 PM
Physics Building, Room 204

## "What are Gravitational Waves telling us about Theoretical Physics "

Nicolas Yunes , Montana State University
[Host: Kent Yagi]
ABSTRACT:

The recent gravitational wave observations of the collision of black holes and of neutron stars have allowed us to pierce into the extreme gravity regime, where gravity is simultaneously unfathomably large and wildly dynamical.  These waves encode a trove of information about physics that is prime for the taking, including potential revelations about the validity of Einstein's theory of General Relativity and about nuclear physics in the extreme gravity regime. In this talk, I will describe some of the inferences we can make on both theoretical and nuclear physics from current and future gravitational wave observations.

Colloquium
Friday, April 6, 2018
3:30 PM
Physics Building, Room 203

Joint Colloquium with Physics and Astronomy/NRAO

## "Chasing Relativistic Electrons in Topological Quantum Materials"

Adam Kaminski , Iowa State and Ames Lab.
[Host: Utpal Chatterjee]
ABSTRACT:

The discovery of Dirac fermions in graphene has inspired a search for Dirac and Weyl semimetals in three dimensions thereby making it possible to realize exotic phases of matter first proposed in particle physics. Such materials are characterized by the presence of nontrivial quantum electronic states, where the electron’s spin is coupled with its momentum and Fermi surfaces are no longer closed contours in the momentum space, but instead consist of disconnected arcs. This opens up the possibility for developing new devices in which information is stored and processed using spin rather than charge. Such platforms may significantly enhance the speed and energy efficiency of information storage and processing. In this talk we will discuss the electronic properties of several of newly discovered tellurium based topological quantum materials. In WTe2 we have observed a topological transition involving a change of the Fermi surface topology (known as a Lifshitz transition) driven by temperature. The strong temperature-dependence of the chemical potential that is at the heart of this phenomenon is also important for understanding the thermoelectric properties of such semimetals. In a close cousin, MoTe2, by using high-resolution laser based Angle Resolved Photoemission Spectroscopy (ARPES) we identify Weyl points and Fermi surface arcs, showing a new type of topological Weyl semimetal with electron and hole pockets that touch at a Weyl point. I will also present evidence for a new topological state in PtSn4, that manifests itself by presence of set of extended arcs rather than Dirac points, and so far is not yet understood theoretically. These results open up new directions for research aimed at enhancing topological responsiveness of new quantum materials.

SLIDESHOW:
Colloquium
Friday, March 30, 2018
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Statistical mechanics for networks of real neurons"

William Bialek , Princeton University
[Host: Marija Vucelja]
ABSTRACT:

Thoughts, memories, percepts, and actions all result from the interactions among large numbers of neurons.  Physicists have long hoped that these emergent behaviors could be described using ideas from statistical mechanics.  Recent experimental developments have made it possible to monitor, simultaneously, the electrical activity in hundreds or even thousands of cells.  I will describe surprisingly simple statistical physics models that provide a detailed, quantitative account of these data, and then turn to renormalization group ideas that allow us to search explicitly for some underlying simplicity.  There are signs that real networks are described by non-trivial fixed points, setting the stage for more ambitious theorizing.

http://www.princeton.edu/~wbialek/wbialek.html

SLIDESHOW:
Colloquium
Friday, March 23, 2018
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "The Physics of Life"

William Bialek , Princeton University
[Host: Marija Vucelja]
ABSTRACT:

In the four hundred years since Galileo, the physics community has constructed a remarkably successful mathematical description of the world around us.  From deep inside the atomic nucleus to the structure of the universe on the largest scales, from the flow air over the wing of an airplane to the flow of electrons in a computer chip, we can predict in detail what we see, and what will happen when we look in places we have never looked before.  What are the limits to this predictive power?  In particular, can we imagine a theoretical physicist’s approach to the complex and diverse phenomena of the living world?  Is there something fundamentally unpredictable about life, or are we missing some deep theoretical principles that could bring the living world under the predictive umbrella of physics?  Exploring this question gives us an opportunity to reflect on what we expect from our scientific theories, and on many beautiful phenomena.  I hope to leave you with a deeper appreciation for the precision of life’s basic mechanisms, and with optimism about the prospects for better theories.

VIDEO:
Colloquium
Thursday, March 22, 2018
7:00 PM
Chemistry , Room 402

Hoxton Lecture

Slideshow (PDF)

## "Multi-messenger Astrophysics in Light of LIGOâs Recent Discoveries"

Imre Bartos , University of Florida
[Host: Kent Yagi]
ABSTRACT:

The recent discoveries of gravitational waves unveiled numerous opportunities in astrophysics, as well as in the study of the cosmos and the laws of physics.  In particular, the multi-messenger detection of binary neutron-star merger GW170817 through gravitational waves and across the electromagnetic spectrum already delivered several important results. I will outline what we learned from GW170817 so far (its remnant is still observable!), along with the opportunities and challenges of near-future multi-messenger observations that will broaden our horizon with gravitational waves in the next few years.  We can expect the proliferation of detected binary neutron star and binary black hole mergers, along with the large-scale efforts to rapidly identify the electromagnetic and neutrino counterparts of these events.  Frequent multi-messenger observations will enable the study of exceptional events, source populations, and sufficient statistics to probe new physics and cosmology.

Colloquium
Friday, March 16, 2018
3:30 PM
Physics Building, Room 203

Joint Colloquium with Physics and Astronomy/NRAO

 Available Colloquium Wednesday, March 14, 2018 3:30 PM Physics Building, Room 204 Special Seminar with Q&A Session  Add to your calendar

## "Quantum gas microscopy of many-body dynamics in Fermi-Hubbard and Ising systems"

Peter Schauss , Princeton University
[Host: Bob Jones]
ABSTRACT:

The ability to probe and manipulate cold atoms in optical lattices at the atomic level using quantum gas microscopes enables quantitative studies of quantum many-body dynamics. While there are many well-developed theoretical tools to study many-body quantum systems in equilibrium, gaining insight into dynamics is challenging with available techniques. Approximate methods need to be benchmarked, creating an urgent need for measurements in experimental model  systems. In this talk, I will discuss two such measurements. First, I will present a study that probes the relaxation of density modulations in the doped Fermi-Hubbard model. This leads to a hydrodynamic description that allows us to determine the conductivity. We observe bad metallic behavior that we compare to predictions from finite-temperature Lanczos calculations and dynamical mean field theory. Second, I introduce a new platform to study the 2D quantum Ising model. Via optical coupling of atoms in an optical lattice to a low-lying Rydberg state, we observe quench dynamics in the resulting Ising model and prepare states with antiferromagnetic correlations.

Colloquium
Friday, March 2, 2018
3:30 PM
Physics Building, Room 204

## "Optical and transport properties of geometric metals"

Dmytro Pesin , University of Utah
[Host: Israel Klich ]
ABSTRACT:

The effects of band geometry on measurable properties of electronic systems have been one of the central subjects in the recent history of condensed matter physics. In this talk, I will describe how non-trivial topology and, more generally, geometry of gapless electronic phases manifest in their optical and transport characteristics.  The main focus of the talk will be on optical anomalous Hall effect and optical activity of Weyl metals, kinetic magnetoelectric effect in noncentrosymmetric conductors, as well as disorder physics in these materials.

Colloquium
Thursday, March 1, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Quantum Mixology: Creating Novel Interacting Bose-Fermi Mixtures with Cs and Li"

Brian DeSalvo , University of Chicago
[Host: Bob Jones]
ABSTRACT:

A gas of atoms cooled to sufficiently low temperature will form either a Bose-Einstein condensate (BEC) or a degenerate Fermi gas (DFG) depending on the quantum statistics of the constituent particles. But what happens when you combine a BEC and a DFG in an optical trap and add a healthy dose of interspecies interactions? Mean-field theory predicts three possible outcomes: a miscible mixture for weak interactions, complete demixing for strong repulsive interactions, or a spectacular collapse due to the loss of mechanical stability for strong attractive interactions. In this talk, I will discuss our efforts to answer this question experimentally in the specific case where the bosons are much heavier than the fermions. To this end, we have created the first quantum degenerate mixture of bosonic 133Cs and fermionic 6Li and used an interspecies Feshbach resonance to tune the interactions between the bosons and fermions. For attractive interspecies interactions, we find two surprising results. First,  we show that a degenerate Fermi gas of Li can be trapped by a Cs BEC, even in the absence of external potentials. Second, for strong attractive interactions where collapse is predicted, we observe no such instability. I will discuss the mechanisms at play to explain these results and comment on current and future studies delving deeper into these unexpected regimes.

Colloquium
Friday, February 23, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "New Frontiers of Electromagnetic Phenomena at the Nanoscale"

[Host: Bob Jones]
ABSTRACT:

Optics and photonics today enjoy unprecedented freedom. The ability to synthesize arbitrary light fields (through wavefront shaping) and the ability to design structures at the subwavelength scale (through nanofabrication) enable us to realize phenomena that could only be imagined in the past. In this talk, I will present several experiments and related theory that demonstrate exciting new phenomena which were previously inaccessible. A) Conventional textbook wisdom is that waves cannot be perfectly confined within the continuum spectrum of an open systems. Exceptions called “bound states in the continuum” were hypothesized by von Neumann and Wigner [1] but not realized. I will describe the first realization of such unusual states [2] and their manifestation as polarization vortices protected by topologically conserved “charges” [3]. B) Our ability to control radiation also enables the realization of non-Hermitian phenomena with no counterpart in closed systems. I will show how non-Hermiticity generates unique topologies in photonic band structures and lead to enhanced lightmatter interactions [4,5]. C) Strong disorder in naturally occurring light-scattering media allows us to study mesoscopic physics in a new arena. I will describe the control of optical transport via wavefront shaping, and how the long-range correlations between multiply scattered photons enable us to simultaneously control orders of magnitudes more degrees of freedom than previously thought possible [6,7].

[1] C. W. Hsu*, B. Zhen* et al., Nature Reviews Materials 1, 16048 (2016).

[2] C. W. Hsu*, B. Zhen* et al., Nature 499, 188 (2013).

[3] B. Zhen*, C. W. Hsu* et al., Phys. Rev. Lett. 113, 257401 (2014).

[4] B. Zhen*, C. W. Hsu* et al., Nature 525, 354 (2015).

[5] H. Zhou et al., Science, eaap9859 (2018).

[6] C. W. Hsu et al., Phys. Rev. Lett. 115, 223901 (2015).

[7] C. W. Hsu et al., Nature Physics 13, 497 (2017).

Colloquium
Monday, February 19, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Topological and nonreciprocal dynamics in an optomechanical system"

Haitan Xu , Yale University
[Host: Bob Jones]
ABSTRACT:

Non-Hermitian systems exhibit rich physical phenomena that open the door to qualitatively new forms of control. In this talk, I will introduce our recent work on topological and nonreciprocal dynamics in a non-Hermitian optomechanical system. Specifically, we realized topological energy transfer between nearly degenerate modes by adiabatically encircling an exceptional point (a singularity of the complex spectrum). We also demonstrated that this energy transfer is non-reciprocal: a given topological operation can only transfer energy in one direction. We have extended the topological and nonreciprocal dynamics to highly non-degenerate modes by exploiting a generic form of nonlinearity, which should allow these effects to be exploited in a very wide range of physical systems. In addition, we realized nonreciprocal dynamics by optomechanical interference.

Colloquium
Friday, February 16, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Quantum Molecular Dynamics of Strongly Correlated Electron Materials"

Gia-Wei Chern , UVA-Department of Physics
ABSTRACT:

I will present a new formulation of quantum molecular dynamics for strongly correlated materials. Our novel scheme enables the study of the dynamical behavior of atoms and molecules with strong electron correlations. In particular, our scheme is based on the efficient Gutzwiller method that goes beyond the conventional mean-field treatment of the intra-atomic electron repulsion and captures crucial correlation effects such as band narrowing and electron localization. We use Gutzwiller quantum molecular dynamics to investigate the Mott metal-insulator transition in the liquid phase of a single-band metal and uncover intriguing structural and transport properties of the atoms. I will also discuss future plans for large-scale dynamical simulations of strongly correlated systems.

Colloquium
Monday, February 12, 2018
3:30 PM
Physics Building, Room 204

## "A Rare and Prolific r-process Event Preserved in an Ultra-Faint Dwarf Galaxy"

Alexander Ji , Carnegie Observatories
[Host: Xiaochao Zheng]
ABSTRACT:

The heaviest elements in the periodic table are synthesized through the rapid neutron-capture process (r-process), but the astrophysical site producing these elements has been a long-standing conundrum. Ultra-faint dwarf galaxies contain a simple fossil record of early chemical enrichment that provide an ideal laboratory to investigate the origin of r-process elements. Previous measurements found very low levels of neutron-capture elements in ultra-faint dwarfs, preferring supernovae as the r-process site. I present high-resolution chemical abundances of nine stars in the recently discovered ultra-faint dwarf Reticulum II, which display extremely enhanced r-process abundances 2-3 orders of magnitude higher than the other ultra-faint dwarfs. Stars with such extreme r-process enhancements are only rarely found in the Milky Way halo. The r-process abundances imply that the neutron-capture material in Reticulum II was synthesized in a single prolific event that is incompatible with r-process yields from ordinary core-collapse supernovae but consistent with a neutron star merger. Together with the recent gravitational wave observations of a neutron star merger and its electromagnetic afterglow, it is now clear that neutron star mergers dominate cosmic production of r-process elements.

Colloquium
Friday, February 9, 2018
3:30 PM
Physics Building, Room 203

Joint Colloquium with Physics and Astronomy/NRAO

## "Electron hydrodynamics in solid-state physics"

Thomas Scaffidi , University of California, Berkeley
[Host: Israel Klich]
ABSTRACT:

Wolfgang Pauli called solid-state physics "the physics of dirt effects", and this name might appear well-deserved at first sight since transport properties are more often than not set by extrinsic properties, like impurities. In this talk, I will present solid-state systems in which electrons behave hydrodynamically, and for which transport properties are instead set by intrinsic properties, like the viscosity. This new regime of transport opens the way for a “viscous electronics”, and provides a new angle to study how quantum mechanics can constrain and/or enrich hydrodynamics.

Colloquium
Thursday, February 8, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "A programmable quantum computer based on trapped ions"

Norbert Linke , Joint Quantum Institute, University of Maryland, and NIST
[Host: Bob Jones]
ABSTRACT:

Quantum computers can solve certain problems more efficiently than any classical computer. Trapped ions are a promising candidate for realizing such a system. We present a modular quantum computing architecture comprised of a chain of 171Yb+ ions with individual Raman beam addressing and individual readout [1]. We use the transverse modes of motion in the chain to produce entangling gates between any qubit pair. This creates a fully connected system which can be configured to run any sequence of single- and two-qubit gates, making it in effect an arbitrarily programmable quantum computer that does not suffer any swap-gate overhead [2].
Recent results from different quantum algorithms on five and seven ions will be presented [3,4], including a quantum error detection protocol that fault-tolerantly encodes a logical qubit [5]. I will also discuss current work and ideas to scale up this architecture.

[1] S. Debnath et al., Nature 563:63 (2016).
[2] NML et al., PNAS 114 13:3305 (2017).
[3] C. Figgatt et al., Nat. Communs. 8, 1918 (2017).
[4] NML et al., arXiv:1712.08581 (2017)
[5] NML et al., Sci. Adv. 3, 10 (2017).

Colloquium
Wednesday, February 7, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Quantum sensing in a new single-molecule regime"

Peter Maurer , Stanford University
[Host: Bob Jones]
ABSTRACT:

Quantum optics has had a profound impact on precision measurements, and recently enabled probing various physical quantities, such as magnetic fields and temperature, with nanoscale spatial resolution. Such advancements in ‘quantum sensing’ have brought the elusive dream of performing nuclear magnetic resonance spectroscopy (NMR) on individual biomolecules closer to reality. In my talk, I will discuss the development and application of novel quantum metrological technologies to study biological systems at a single-molecule level. I will start with a general introduction to quantum sensing, with a focus on the measurement of magnetic fields at a nanoscale. I will then show how we utilize such sensing techniques to control the temperature profile in living systems with subcellular resolution. Finally, I will provide an outlook on how quantum sensing and single-molecule biophysics can be utilized to perform NMR spectroscopy with unprecedented sensitivity, possibly down to the level of individual biomolecules.

Colloquium
Monday, February 5, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Topological Superconductivity From Electronic Interactions"

Yuxuan Wang , UIUC
[Host: Israel Klich ]
ABSTRACT:

Topological superconductors exhibit exotic Majorana modes at the boundaries and vortices, and can provide important applications in quantum computing. In addition to usual path of “engineering” topological superconductivity with heterostructure of conventional superconductors, we show that intrinsic topological superconductivity can also be naturally realized through electron-electron interactions. Specifically, we analyze the topological superconducting state that emerges near the onset of an inversion-breaking electronic order. Other than topological superconductivity, we show that the system has an enhanced U(1)xU(1) symmetry as well as a rich phase diagram. We address the relevance of our results with recent experiments in Cd2Ce2O7 and half-Heusler superconductors. We argue that important progress can be made at the intersection of topological superconductivity and unconventional superconductivity.

Colloquium
Friday, February 2, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Imprints of complex landscapes on glassy materials"

Sho Yaida , Duke University
[Host: Israel Klich ]
ABSTRACT:

Amorphous solids are omnipresent in everyday life, from window glasses to plastics to piles of sand. Yet our understanding of their properties lags far behind that of their crystalline counterparts. Recent advances are rapidly changing the way in which we understand these materials. This talk overviews two such advances: (i) the algorithmic developments that link dramatic slowdown of glass-forming liquids to growing amorphous order, and (ii) the discovery of the critical replica-symmetry-breaking transition within solid glasses. Taken together, these results reinforce the overriding role of rugged free-energy landscapes in controlling glassiness.

Colloquium
Friday, January 26, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Topological Quantum Chemistry"

Jennifer Cano , Princeton University
[Host: Israel Klich ]
ABSTRACT:

The past decade's apparent success in predicting and experimentally discovering distinct classes of topological insulators (TIs) and semimetals masks a fundamental shortcoming: out of 200,000 stoichiometric compounds extant in material databases, only several hundred of them are topologically nontrivial. Are TIs that esoteric, or does this reflect a fundamental problem with the current piecemeal approach to finding them? To address this, we propose a new and complete electronic band theory that highlights the link between topology and local chemical bonding, and combines this with the conventional band theory of electrons. We classify the possible band structures for all 230 crystal symmetry groups that arise from local atomic orbitals, and show which are topologically nontrivial. We show how our topological band theory sheds new light on known TIs, and demonstrate the power of our method to predict new TIs.

Colloquium
Tuesday, January 23, 2018
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Constraints on multiparticle entanglement"

David Meyer , University of California at San Diego
[Host: Olivier Pfister]
ABSTRACT:

States of a multiparticle quantum system are useful for quantum information processing when they are entangled, i.e., not product states relative to the tensor product decomposition of the Hilbert space corresponding to the particles.  Arbitrary entanglements between parts of a quantum system are not possible, however; they must satisfy certain “monogamy” constraints which limit how much multiple different subsystems can be entangled with one another.  The standard monogamy constraints can be generalized in several ways:  in this talk we’ll tighten some, generalize others to higher dimensional tensor factors, and derive inequalities satisfied by symmetric sets of entanglement measures.  Along the way we’ll contrast the quantum results with corresponding statements about classical random variables.

https://math.ucsd.edu/people/profiles/david-meyer/

Colloquium
Friday, January 19, 2018
3:30 PM
Physics Building, Room 204

## "Entanglement, chaos and order"

Xiaoliang Qi , Stanford University
[Host: Israel Klich ]
ABSTRACT:

In classical mechanics, chaos refers to the phenomenon that an arbitrarily small perturbation leads to a dramatic change at a later time. The analogous phenomenon in quantum mechanics---quantum chaos is generic in many-body systems. Although chaos makes it difficult to solve the many-body problem exactly, it actually provides new knowledge about dynamics of the system, such as thermalization. In understanding quantum chaos and thermalization, the concept of quantum entanglement plays an essential role. In this talk, I will discuss the connection between several related phenomena, including the dynamics of quantum entanglement, thermalization of isolated systems, and measure of quantum chaos. As a concrete model to study quantum chaos, I will discuss the Sachdev-Ye-Kitaev (SYK) model and its generalizations. This model provides an example of strongly correlated systems in which new kinds of "order" emerges from chaos. Entanglement dynamics in this model suggests an interesting interplay between thermalization and many-body localization.

References: arXiv:1511.04021

arXiv:1708.00871

SLIDESHOW:
Colloquium
Friday, December 1, 2017
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Recent Advances on the Glass Problem"

Patrick Charbonneau , Duke University
[Host: Marija Vucelja]
ABSTRACT:

Recent theoretical advances in the mean-field theory of glasses predict the existence, deep in the glass phase, of a novel phase transition, a so-called Gardner transition. This transition signals the emergence of a complex free energy landscape composed of a marginally stable hierarchy of sub-basins. It is also thought to be the onset of the anomalous thermal and transport properties of amorphous systems, and to ultimately lead to the unusual critical behavior at jamming. In this talk, I will present an overview of our recent theoretical and numerical advances in capturing and characterizing this novel materials feature.

Colloquium
Friday, November 17, 2017
3:30 PM
Physics Building, Room 204

## "Bad Metal Behavior and Mott Quantum Criticality"

Vladimir Dobrosavljevic , Florida State University
[Host: Gia-Wei Chern]
ABSTRACT:

According to early ideas of Mott and Anderson, the interaction-­driven metal-­insulator transition “the Mott transition“ remains a sharp T=0 phase transition even in absence of any spin or charge ordering.  Should this phase transition be regarded as a quantum critical point?  To address this question, here we examine the phase diagram and transport properties of the maximally frustrated half-­filled Hubbard model, in the framework of dynamical mean-­field theory (DMFT).  We identify a quantum Widom line (QWL) which defines the center of the corresponding quantum critical region associated with Mott metale insulator transition for this model.  The evolution of resistivity with temperature is then evaluated along trajectories following (parallel to) the QWL, displaying remarkable scaling behavior characteristic of quantum criticality.  Precisely this kind of behavior was found in very recent experiments on organic Mott systems [1,2].  In the case of the doping-driven Mott transition, we show that the mysterious Bad Metal behavior (T-linear resistivity around the Mott-Ioffee- Regel limit) coincides with the Quantum Critical region of the Mott transition.

[1] Quantum criticality of Mott transition in organic materials, Tetsuya Furukawa, Kazuya Miyagawa, Hiromi Taniguchi, Reizo Kato & Kazushi Kanoda, Nature Physics, 9 Feb.  2015; doi:10.1038/nphys3235.

http://condensedconcepts.blogspot.com/2015/03/quantum-criticality-near-mott.html

Colloquium
Friday, November 10, 2017
3:30 PM
Physics Building, Room 204

## "APS Bridge Program: Changing the Face of Physics Graduate Education"

Ted Hodapp , APS Bridge Program
[Host: Olivier Pfister]
ABSTRACT:

In nearly every science, math, and engineering field there is a significant falloff in participation by underrepresented minority (URM) students who fail to make the transition between undergraduate and graduate studies.  The American Physical Society (APS) has realized that a professional society can erase this gap by acting as a national recruiter of URM physics students and connecting these individuals with graduate programs that are eager to a) attract motivated students to their program, b) increase domestic student participation, and c) improve the diversity of their program.  Now in its fifth year the APS has placed enough students into graduate programs nationwide to eliminate this achievement gap.  The program has low costs, is popular among graduate programs, and has inspired other departments to adopt practices that improve graduate admissions and student retention. This presentation will review project activities, present data that demonstrate effectiveness, and discuss future actions.

This material is based upon work supported in part by the National Science Foundation under Grant No. (NSF-1143070).

Colloquium
Friday, November 3, 2017
3:30 PM
Physics Building, Room 204

## "Lifting the Bandwidth Limit of Optical Homodyne Measurement - A Key for Broadband Quantum Information"

Avi Pe'er , Bar Ilan University
[Host: OSA/SPIE Student Chapter]
ABSTRACT:

Homodyne measurement is a corner-stone of quantum optics. It measures the fundamental variables of quantum electrodynamics - the quadratures of light, which represent the cosine-wave and sine-wave components of an optical field. The quadratures constitute the quantum optical analog of position and momentum in mechanics and obey quantum uncertainty, indicating the inherent inability to measure both simultaneously. The homodyne process, which extracts a chosen quadrature amplitude by correlating the optical field against an external quadrature reference (local-oscillator, LO), forms the backbone of coherent detection in physics and engineering, and plays a central role in quantum information processing. Homodyne can reveal non-classical phenomena, such as squeezing of the quadrature uncertainty; It is used in tomography to fully characterize quantum states of light; Homodyne detection can generate non-classical states, provide local measurements for teleportation and serve as a major detector for quantum key distribution (QKD) and quantum computing. Yet, standard homodyne suffers from a severe bandwidth limitation. While the bandwidth of optical states can easily span many THz, standard homodyne detection is inherently limited to the electrically accessible, MHz to GHz range, leaving a dramatic gap between the relevant optical phenomena and the measurement capability. This gap impedes effective utilization of the huge bandwidth resource of optical states and the potential enhancement of the information throughput \emph{by several orders of magnitude} with parallel processing in quantum computation, QKD and other applications of quantum squeezed light. Here we demonstrate a fully parallel optical homodyne measurement across an arbitrary optical bandwidth, effectively lifting the bandwidth limitation completely. Using optical parametric amplification, which amplifies one quadrature while attenuating the other, we measure two-mode quadrature squeezing of 1.7dB below the vacuum level simultaneously across a bandwidth of 55THz using a single LO - the pump. This broadband parametric homodyne measurement opens a wide window for parallel processing of quantum information.

Yaakobv Shaked, Yoad Michael, Rafi Vered, Leon Bello, Michael Rosenbluh and Avi Pe'er, Physics Dept. and BINA center for  Nanotechnology, Bar Ilan University, Ramat Gan 5290002, Israel

Colloquium
Friday, October 27, 2017
3:30 PM
Physics Building, Room 204

## "Tomography of the Atomic Nucleus"

Simonetta Liuti , UVA-Physics
[Host: Joe Poon]
ABSTRACT:

The history of our exploration of subatomic matter has witnessed a major breakthrough with every new probe being introduced. In the 1950’s Hofstadter and collaborators using elastic electron scattering measured for the first time the electromagnetic form factors of nucleons and nuclei and provided the first information on the nuclear spatial charge and magnetization distributions. In the late 1960’s and early 70’s, Friedman, Kendall and Taylor using Deep Inelastic Scattering of electrons off the nucleon, discovered its underlying quark structure displayed in their longitudinal momentum distributions.

I will discuss probes at the next frontier that will allow us to access dynamically correlated distributions in both momentum and coordinate space -- the Wigner distributions -- at the femtoscale. Deeply Virtual Compton Scattering, namely a high energy lepton scattering off a nucleon target producing a high energy real photon and a small angle recoil proton, is one of such probes. I will explain how a detailed mapping of the quarks and gluons in the nucleon and nucleus in phase space, or a phase-space tomography, besides providing for the first time images of quarks and gluons spatial distributions, is essential for understanding the so far elusive nucleon mass and spin decompositions in terms of its quark and gluon components.

Colloquium
Friday, October 20, 2017
3:30 PM
Physics Building, Room 204

## "All-optical Switching for Photonic Quantum Networks"

Prem Kumar , Northwestern University
[Host: Olivier Pfister]
ABSTRACT:

Quantum internet of the future will require device functionalities that implicitly respect the fundamental facts such as quantum information cannot be copied, and cannot be measured precisely. A quantum repeater, for example,—analog of an optical amplifier that enabled global reach of the ubiquitous Internet connectivity we enjoy today—is yet to be demonstrated, although recent years have seen tremendous progress. Many other device functionalities—switches, routers, format converters, etc.—would also be needed that do not unnecessarily disturb or corrupt the quantum information as it flows from one node of the internet to another. In recent years, my group has engineered an all-optical quantum switch that fulfills many of the requirements for distributing quantum information in a networked environment. In this talk, I will present our motivation, design, construction, characterization, and utilization of such a switch in near-term networked quantum applications.

SLIDESHOW:
Colloquium
Friday, October 13, 2017
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Looking for New Physics with the Weak Interaction in Electron Scattering: Recent Results from Qweak and Future Perspectives"

Kent Paschke , UVA-Physics
[Host: Joe Poon]
ABSTRACT:

The measurement of the violation of parity symmetry in electron scattering has proven to be a powerful technique for exploring nuclear matter and searching for new fundamental forces. In the Standard Model of particle physics, parity violation can only occur through the weak interaction. Precision measurements of this symmetry breaking can test the completeness of this description of the weak force at low energies. I will describe the result of one such measurement - the recently completed Qweak experiment - along with the experimental challenges and triumphs.  Future measurements in the field of parity-violating electron scattering will also be reviewed, including other Standard Model tests and experiments using the weak force to determine the size of a heavy atomic nucleus.

SLIDESHOW:
Colloquium
Friday, October 6, 2017
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Peeling the Atomic Onion"

Xiaochao Zheng , UVA-Physics
[Host: Joe Poon]
ABSTRACT:

The word "atom" (a-tomos) originates from ancient Greek philosophers, who argued that objects can be eventually divided into discrete, small particles, beyond which matter is no longer cuttable.  Our search for the answer to "What the matter is made of" has gone a long way, from the first experimental evidence of atoms in the 1800's, to Rutherford's alpha scattering on gold foils, to modern day's linear accelerators looking into the atomic nucleus. We now understand that matter is made of quarks and leptons, currently named elementary particles (objects of no size) that form the foundation of the Standard Model of Particle Physics. However, if we look back at this journey, one may wish to oppose the view of the ancient Greeks and argue that quarks and leptons cannot be the end of the story, that our quest for peeling the atomic onion may be a timeless journey.

I will discuss the frontier research in electron scattering at the GeV energy level. I will focus on parity violation in electron scattering off the proton and the neutron and the extraction of neutral-weak effective couplings between electrons and quarks, and show how such high precision measurements are now helping us venturing further into the study of subatomic structure.

SLIDESHOW:
Colloquium
Friday, September 29, 2017
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Future directions in gravitational-wave detection"

Nergis Mavalvala , M.I.T.
[Host: Cass Sackett]
ABSTRACT:

The Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves for the first time in 2015. Since then there have been a couple more detections of binary black hole mergers. I will discuss the instruments that made these discoveries, the science so far, and plans for future improvements and upgrades to LIGO.

VIDEO:
Colloquium
Friday, September 22, 2017
3:30 PM
Physics Building, Room 204

## "The Warped Universe: the one hundred year quest to discover Einsteinâs gravitational waves"

Nergis Mavalvala , M.I.T.
ABSTRACT:

In 2016, scientists announced the first ever detection of gravitational waves from colliding black holes, launching a new era of gravitational wave astrophysics. Gravitational waves were predicted by Einstein a hundred years earlier. I will describe the science, technology, and human story behind these discoveries that provide a window into some of the most violent and warped events in the Universe.

Colloquium
Thursday, September 21, 2017
7:00 PM
Chemistry Building, Room 402

Special Colloquium and Hoxton Lecture

## "Tune-out wavelength spectroscopy: a new technique to characterize atomic structure"

Cass Sackett , UVA-Physics
[Host: Joe Poon]
ABSTRACT:

When you shine a laser on an atom, the electric field of the light induces a dipole moment, resulting in an energy shift. The dipole can be either parallel or anti-parallel to the field, depending on the frequency of the light. This corresponds to negative or positive energies. At certain frequencies, however, the induced dipole is zero. The corresponding light wavelength is called a tune-out wavelength. The location of the various tune-out wavelengths depend on the electronic wave function in the atom, particularly the dipole matrix elements . So by measuring the tune-out wavelength, the dipole matrix elements can be determined more accurately than by conventional techniques. This is useful because the dipole matrix elements are also used to relate precision atomic experiments like parity violation to fundamental particle properties like the weak mixing angle. We have developed a new technique for measuring  tune-out wavelengths, which should improve our knowledge of many matrix elements by an order of magnitude or more. We hope that this will support new generations of precision atomic measurements.

SLIDESHOW:
Colloquium
Friday, September 15, 2017
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Origin of Long Lifetime of Band-Edge Charge Carriers in Organic-Inorganic Lead Iodide Perovskites"

Tianran Chen , UVA-Physics
[Host: Seunghun Lee]
ABSTRACT:

Long carrier lifetime is what makes hybrid organic-inorganic perovskites high performance photovoltaic materials. Several microscopic mechanisms behind the unusually long carrier lifetime have been proposed, such as formation of large polarons, Rashba effect, ferroelectric domains, and photon recycling. Here, we show that the screening of band-edge charge carriers by rotation of organic cation molecules can be a major contribution to the prolonged carrier lifetime. Our results reveal that the band-edge carrier lifetime increases when the system enters from a phase with lower rotational entropy to another phase with higher entropy. These results imply that the recombination of the photo-excited electrons and holes is suppressed by the screening, leading to the formation of polarons and thereby extending the lifetime. Thus, searching for organic-inorganic perovskites with high rotational entropy over a wide range of temperature may be a key to achieve superior solar cell performance.

Colloquium
Friday, September 8, 2017
3:30 PM
Physics Building, Room 204

 Physics Forum Colloquium Friday, September 1, 2017 3:30 PM Physics Building, Room 203 Special Physics Forum for Faculty, Students, and Staff  Add to your calendar

## "Available"

Colloquium
Friday, August 25, 2017
3:30 PM
Physics Building, Room 204

## "Making Neutrino Astronomy Real"

John Beacom , Ohio State
[Host: Craig Group]
ABSTRACT:

For over 50 years, people have been discussing the promise of high-energy neutrino astronomy.  For most of that time, wholesale theoretical conjecture was unmatched by even a trifling return of measured experimental facts.  Then in 2013, the IceCube neutrino observatory discovered astrophysical neutrinos with energies up to fifteen orders of magnitude above those of visible light.  What does this mean for understanding astrophysical sources, the properties of neutrinos, and the contents of the Universe?

Colloquium
Friday, April 28, 2017
3:30 PM
Physics Building, Room 204

 Kerry Vahala , Caltech [Host: OSA/SPIE Student Chapter] Colloquium Wednesday, April 26, 2017 3:30 PM Physics Building, Room 204  Add to your calendar
Annual Physics Day
ABSTRACT:

# Observing the Universe with Physics

Wednesday, April 26, 2017, 7:00 p.m.
Physics Building, Room 203

A Family-Oriented Event! Free! Open to the Public!
Come see an hour of exciting and intriguing demonstrations!

For a map showing the location of the Physics Building, see:
http://www.virginia.edu/webmap/popPages/76-PhysicsBldg_Jesse.html

Colloquium
Wednesday, April 26, 2017
7:00 PM
Physics Building, Room 204

Annual Physics Day Show

## "Probing Molecular Dynamics from Within using FELs"

Nora Berrah , University of Connecticut
[Host: Despina Louca]
ABSTRACT:

Short x-ray pulses from free electron lasers (FELs) open a new regime for all scientific research. The first x-ray FEL, the Linac Coherent Light Source (LCLS) at the SLAC National Laboratory on the Stanford campus, provides intense short pulses that allow the investigation of ultrafast non-linear and multi-photon processes, including time-resolved investigations in molecules. We will report on the femtosecond response of molecules to the ultra-intense, ultrafast x-ray radiation from FELs as well as on time-resolved investigation using x-ray pump-x-ray probe techniques.

Colloquium
Friday, April 21, 2017
3:30 PM
Physics Building, Room 204

## "Negative resistance and other wonders of viscous electronics in graphene"

Gregory Falkovich , Weizmann Institute
[Host: Marija Vucelja]
ABSTRACT:

Quantum-critical strongly correlated systems feature universal collision-dominated collective transport. Viscous electronics is an emerging field dealing with systems in which strongly interacting electrons flow like a fluid. We identified vorticity as a macroscopic signature of electron viscosity and linked it with a striking macroscopic DC transport behavior: viscous friction can drive electric current against an applied field, resulting in a negative resistance, recently measured experimentally in graphene. I shall also describe current vortices, expulsion of electric field, conductance exceeding the fundamental quantum-ballistic limit and other wonders of viscous electronics. Strongly interacting electron-hole plasma in high-mobility graphene affords a unique link between quantum-critical electron transport and the wealth of fluid mechanics phenomena.

http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3667.html

https://arxiv.org/abs/1607.00986

http://arxiv.org/abs/1607.07269

SLIDESHOW:
Colloquium
Friday, April 14, 2017
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "[CANCELED] Engineering Quantum Thermal Machines"

Adolfo Del Campo , University of Massachusetts
[Host: Israel Klich ]
ABSTRACT:

Quantum thermodynamics has emerged as an interdisciplinary research field in quantum science and technology with widespread applications. Yet, the identification of scenarios characterized by quantum supremacy -a performance without match in the classical world- remains challenging. In this talk I shall review recent advances in the engineering and optimization of quantum thermal machines. I will show that nonadiabatic many-particle effects can give rise to quantum supremacy in finite-time thermodynamics [1]. Tailoring such nonadiabatic effects by making use of shortcuts to adiabaticity, quantum heat engines can be operated at maximum efficiency and arbitrarily high output power [2]. A thermodynamic cost of these shortcuts will be elucidated by analyzing the full work distribution function and introducing a novel kind of work-energy uncertainty relation [3]. I shall close by discussing the identification of scenarios with a quantum-enhanced performance in thermal machines run over many cycles [4].

Bibliography:
[1] J. Jaramillo, M. Beau, A. del Campo, New J. Phys. 18, 075019 (2016).
[2] M. Beau, J. Jaramillo, A. del Campo, Entropy 18, 168 (2016).
[3] K. Funo, J.-N. Zhang, C. Chatou, K. Kim, M. Ueda and A. del Campo, Phys. Rev. Lett, 118, 100602 (2017).
[4] G. Watanabe, B. P. Venkatesh, P. Talkner and A. del Campo, Phys. Rev. Lett. 118, 050601 (2017).

Colloquium
Friday, April 7, 2017
3:30 PM
Physics Building, Room 204

## "Storage at the Threshold: Li-ion Batteries and Beyond"

George Crabtree , Joint Center for Energy Storage Research (JCESR) Argonne National Laboratory and University of Illinois at Chicago
[Host: Bellave Shivaram]
ABSTRACT:

The high energy density and low cost of lithium-ion batteries have created a revolution in personal electronics through laptops, tablets, smart phones and wearables, permanently changing the way we interact with people and information.  We are at the threshold of similar transformations in transportation to electric cars and in the electricity grid to renewable generation, smart grids and distributed energy resources.  Many aspects of these transformations require new levels of energy storage performance and cost that are beyond the reach of Li-ion batteries.  Next generation beyond Li-ion batteries and their potential to meet these performance and cost thresholds will be analyzed.

George Crabtree, Elizabeth Kocs and Lynn Trahey, The energy-storage frontier: Lithium-ion batteries and beyond, MRS Bulletin 40, 1067 (2015)

Bio: George Crabtree is Director of the Joint Center for Energy Storage (JCESR) at Argonne National Laboratory and Professor of Physics, Electrical, and Mechanical Engineering at University of Illinois-Chicago (UIC).  He has wide experience in next-generation battery technology and integrating energy science, technology, policy and societal decision-making. He has led workshops for the Department of Energy on energy science and technology, is a member of the National Academy of Sciences and has testified before the U.S. Congress

Colloquium
Friday, March 31, 2017
9:00 AM
The Rotunda, Room Dome Room

Special Colloquium

## "A New Way to Look at the Sky"

Kirsten Tollefson , Michigan State University
[Host: Chris Neu]
ABSTRACT:

The High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory was completed in March 2015 and is now giving us a new view of the sky. HAWC is a continuously operating, wide field-of-view observatory sensitive to 100 GeV – 100 TeV gamma rays and cosmic rays. It is 15 times more sensitive than previous generation extensive air shower gamma-ray instruments. It serves as a “finder” telescope and monitors the same sky as gamma-ray satellites (Fermi), gravity-wave (LIGO) detectors and neutrino observatories (IceCube) allowing for multi-wavelength and multi-messenger observations.  HAWC hopes to answer questions such as "what is dark matter?” and “where do cosmic rays come from?” by observing some of the most violent processes in our Universe. I will present highlights from HAWC’s first year of operation.

Colloquium
Friday, March 31, 2017
3:30 PM
Physics Building, Room 204

## "Controlling cell size and DNA replication in bacteria - insights from mathematical modeling"

Ariel Amir , Harvard University
[Host: Marija Vucelja]
ABSTRACT:

Understanding how cells control and coordinate the various ongoing cellular processes, such as DNA replication, growth and division is an outstanding fundamental problem in biology. Remarkably, bacterial cells may divide faster than their chromosomes replicate, implying that cells maintain multiple rounds of chromosome replication, and that tight control over DNA replication must be in place. I will show how ideas from statistical mechanics and mathematical modeling can serve as alternative "microscopes" into this problem. Our results suggest that both cell size and chromosome replication may be simultaneously regulated by following a simple control mechanism, in which, effectively, a constant volume is added between two DNA replication initiation events. This model elucidates the experimentally observed correlations between various events in the cell cycle, and explains the exponential dependence of cell size on the growth rate, as well as recent experiments in which cell morphology is perturbed.

http://amir.seas.harvard.edu/

Colloquium
Friday, March 24, 2017
3:30 PM
Physics Building, Room 204

## "Ice Fishing for Neutrinos at the South Pole"

Francis Halzen , UW - Wisconsin
[Host: Craig Group]
ABSTRACT:

The IceCube project at the South Pole has melted eighty-six holes over 1.5 miles deep in the Antarctic icecap for use as astronomical observatories. The project recently discovered a flux of neutrinos reaching us from the cosmos, with energies more than a million times those of the neutrinos produced at accelerator laboratories. These neutrinos are astronomical messengers from some of the most violent processes in the universe--giant black holes gobbling up stars in the heart of quasars and gamma-ray bursts, the biggest explosions since the Big Bang.

In a special public lecture, brought to you by the departments of physics, astronomy, and NRAO Francis Halzen, Gregory Breit Professor and Hilldale Professor of Physics at UW-Madison and the principal investigator of IceCube, will tell the story of the IceCube telescope and discuss highlights from recent scientific results.

SLIDESHOW:
Colloquium
Thursday, March 23, 2017
7:00 PM
The Rotunda, Room Dome Room

Special Colloquium

Slideshow (PDF)

## "Manipulating atoms with light: from spectroscopy to atomtronics"

Bill Phillips , NIST
[Host: Sanjay Khatri - OSA Student Chapter]
ABSTRACT:

Physicists have used light and its polarization to elucidate the internal state of atoms since the 19th century.  Early in the 20th century, the momentum of light was used to change the center-of-mass motion of atoms.  The latter part of the 20th century brought optical pumping, coherent laser excitation, and laser cooling and trapping as tools to manipulate both the internal and external states of atoms.  Atom optics techniques like diffraction of atoms from light provided the elements needed for atom-wave interferometers.  Bose-Einstein condensation created atomic samples having laser-like deBroglie-wave coherence.   Now, in the 21st century, the circulation of superfluid atoms in ring-shaped structures enables “atomtronic” circuitry—an atomic analog of superconduction electric circuits.  We observe persistent flow of atoms in toroidal traps, and can introduce a weak-link (a kind of Josephson junction) that allows control of the quantized circulation of atoms.

VIDEO:
Colloquium
Friday, March 17, 2017
3:30 PM
Physics Building, Room 203

## "From Chirps to Jets: The extreme world of Black Holes and Neutron Stars"

Francois Foucart , Lawrence Berkeley National Lab
[Host: Peter Arnold]
ABSTRACT:

Black holes and neutron stars are extraordinary astrophysical laboratories.

They allow us to test the laws of gravity and nuclear physics in extreme environments which cannot be reproduced on Earth. In this talk, I will discuss efforts to model these compact objects in two classes of astrophysical systems: mergers of black hole-neutron star and neutron star-neutron star binaries, and accretion disks around supermassive black holes. The first are powerful sources of gravitational waves, and emit bright electromagnetic transients. In the advanced gravitational wave detector era, they will provide us with new information about general relativity, the properties of matter above nuclear density, and the population of black holes and neutron stars. The second will soon be imaged by the Event Horizon Telescope with enough accuracy to resolve the horizon of two black holes, and to study the behavior of the nearly collisionless plasma accreting onto them. I will in particular focus on the role of numerical simulations using general relativistic codes, which will play a crucial role in our interpretation of these upcoming observations.

SLIDESHOW:
Colloquium
Wednesday, March 1, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Quantum alchemy for the 21st century: accessing new horizons of quantum many-body dynamics through periodic driving"

Mark Rudner
[Host: Israel Klich ]
ABSTRACT:

Recent work on topological materials has revealed a wide variety of intriguing phenomena that may arise when particles move in "non-trivial" bands.  At the same time, modern advances in experimental capabilities for controlling electronic, atomic, and optical systems open new possibilities for dynamically controlling the behaviors of a range of quantum systems. In this talk I will review the basic ideas behind topological band theory, and then explain how periodic driving can be used to gain dynamical control over the topological properties of quantum matter.  In the driven case, intriguing new types of robust non-equilibrium topological phenomena emerge. To illustrate, I will show how the combination of driving, topology, and interactions can bring about a new regime of universal quantized transport, and discuss potential near-term experimental realizations.

**THE RECEPTION WILL BE HELD AT 3:00PM IN ROOM 313**

Colloquium
Tuesday, February 28, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

## "The Past, Present, and Future of 21cm Cosmology"

[Host: Peter Arnold]
ABSTRACT:

In the next few years, low-frequency radio telescopes will use the 21cm line of neutral hydrogen to make unprecedentedly large maps of our observable Universe. These will provide exquisite constraints on the properties of the first stars and galaxies. Along these lines, I will review recent results from the Precision Array to Probe the Epoch of Reionization (PAPER) experiment, which have begun to shed light on heating processes in the early universe. I will also discuss how comparing theory and observations will become difficult as one enters the regime of “big data” and theoretical models become increasingly complicated. I will describe how machine learning techniques make such comparisons computationally feasible. Finally, I will discuss the recently commenced Hydrogen Epoch of Reionization Array (HERA) experiment, including its forecasted ability to constrain fundamental parameters such as the neutrino mass. Looking to the future, I will highlight additional opportunities to constrain cosmology and particle physics using the 21cm line.

SLIDESHOW:
Colloquium
Monday, February 27, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

 RESERVED Colloquium Friday, February 24, 2017 3:30 PM Physics Building, Room 204  Add to your calendar

## "Progress and challenges in designing a universal Majorana quantum computer"

Torsten Karzig , Station Q, UCSB
[Host: Israel Klich ]
ABSTRACT:

I will discuss a promising design proposal for a scalable topological quantum computer. The qubits are envisioned to be encoded in aggregates of four or more Majorana zero modes, realized at the ends of topological superconducting wire segments that are assembled into superconducting islands with significant charging energy. Quantum information can be manipulated according to a measurement-only protocol, which is facilitated by tunable couplings between Majorana zero modes and nearby semiconductor quantum dots. The key virtue of the proposed architecture is its modular and scalable design and a natural suppression of quasiparticle poisoning by charge protection.

In the second part of the talk I will comment on the importance of elevating these designs to full quantum universality by so called magic state injection. The latter relies on a high fidelity source of specific quantum states and I will point out some of ideas and challenges for providing them.

**THE RECEPTION WILL BE HELD AT 3:00PM IN ROOM 313**

Colloquium
Thursday, February 23, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Gravitational waves from binary black holes across the spectrum"

Michele Vallisneri , Jet Propulsion Laboratory, Caltech
[Host: Peter Arnold]
ABSTRACT:

On September 14, 2015, the two LIGO detectors simultaneously observed a transient gravitational-wave signal, which was named GW150914. The signal fit very precisely the general-relativistic prediction for the inspiral, merger, and ringdown of a pair of stellar-mass black holes, with component masses greater than was thought possible in standard evolution scenarios. This was the first direct detection of gravitational waves and the first observation of a binary black-hole merger. I describe the mechanics and behind-the-scenes of the detection, and its implications for astrophysics and fundamental physics. Two additional black-hole binaries were detected in LIGO's first observing run, and more are expected from current data taking. At the low-frequency side of the gravitational-wave spectrum, signals from massive black-hole binaries are targeted by the space-based observatory LISA, now on track for launch in the early 2030s, and by pulsar-timing arrays, with a positive detection expected in ten years. I discuss the science case, prospects, and requirements of these programs.

**THE RECEPTION WILL BE HELD AT 3:00PM IN ROOM 313**

SLIDESHOW:
Colloquium
Wednesday, February 22, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Bosonic Symmetry Protected Topological States: Theory, Numerics, and Experimental Platform"

Yi-Zhuang You , Harvard University
[Host: Israel Klich ]
ABSTRACT:

Topological phases of matter is an active research area of condensed matter physics. Among various topics, the bosonic symmetry protected topological (BSPT) states have attracted enormous theoretical interest in the last few years. BSPT states are bosonic analogs of topological insulators. The Haldane phase of spin-1 chains is one famous example. I will talk about our recent proposal to realize two-dimensional BSPT states in the twisted bilayer graphene with strong magnetic field, as well as numerical simulations of the lattice model in various parameter regimes. The proposed BSPT state is a quantum spin Hall insulator with bosonic boundary modes only. The bosonic modes are spin and charge collective excitations of electrons. The quantum phase transition between the topological and the trivial phases happens by closing the gap of bosonic modes in the bulk, without closing the single particle gap of electrons, which is fundamentally different from all the well-known topological transitions in free fermion topological insulators. On the theory side, the phase transition is related to topics of deconfined criticality and duality of (2+1)D conformal field theories. The theoretical, numerical and experimental studies will deepen our understanding of quantum phase transitions.

**THE RECEPTION WILL BE HELD AT 3:00PM IN ROOM 313**

Colloquium
Thursday, February 16, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

## " Probing Extreme Gravity with Black Holes and Neutron Stars"

Kent Yagi , Princeton University
[Host: Peter Arnold]
ABSTRACT:

Black holes and neutron stars are extremely compact astrophysical objects that are produced after the death of very massive stars. Due to their large compactness and population, such compact objects offer us excellent testbeds for probing fundamental physics. In this talk, I will focus on probing extreme (strong and dynamical-field) gravity that was previously inaccessible. Regarding black hole based tests of gravity, I will explain how stringently one can probe various fundamental pillars in General Relativity with the recently-discovered gravitational wave events. Regarding neutron star based tests of gravity, I will use approximate universal relations ("I-Love-Q relations") among certain neutron star observables that are almost insensitive to the unknown stellar internal structure, and describe how one can probe extreme gravity by combining future gravitational wave and binary pulsar observations. I will conclude with a summary of important future directions.

SLIDESHOW:
Colloquium
Wednesday, February 15, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Superconductivity from repulsion"

Andrey Chubukov , University of Minnesota
[Host: Genya Kolomeisky]
ABSTRACT:

In my talk, I review recent and not so recent works aiming to understand whether a nominally repulsive Coulomb interaction can by itself give rise to a superconductivity.  I discuss a generic scenario of the pairing by electron-electron interaction, put forward by Kohn and Luttinger back in 1965, and  modern studies of  the electronic mechanisms of superconductivity in the lattice systems which model cuprates,  Fe-pnictides, and  doped graphene.  I show that the pairing in all three classes of materials can be viewed as a lattice version of Kohn-Luttinger physics, despite that the pairing symmetries are different.  I discuss under what conditions the pairing occurs and rationalize the need to do  renormalization-group studies.  I also discuss the interplay between superconductivity and density-wave instabilities.

SLIDESHOW:
Colloquium
Friday, February 10, 2017
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "The Art of Metal Joining and How It's Used NASA Michoud Assembly Facility"

Renee Horton , NASA
ABSTRACT:

Metal joining is a controlled process used to fuse metals. There are several techniques of metal joining of which friction stir welding is one of the more basic forms. Friction stir welding is an innovative weld process that continues to grow in use, in the commercial, defense, and space sectors. It produces high quality and high strength welds in aluminum alloys. The process consists of a rotating weld pin tool that plasticizes material through friction. The plasticized material is welded by applying a high weld forge force through the weld pin tool against the material during pin tool rotation.  Self-reacting friction stir welding (SR-FSW) is one variation of the FSW process developed at the National Aeronautics and Space Administration (NASA) for use in the fabrication of propellant tanks and other areas used on the Space Launch System (SLS)

NASA's SLS is an advanced, heavy-lift launch vehicle which will provide an entirely new capability for science and human exploration beyond Earth's orbit. The SLS will give the nation a safe, affordable and sustainable means of reaching beyond our current limits and open new doors of discovery from the unique vantage point of space.

SLIDESHOW:
Colloquium
Tuesday, February 7, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Bouncing"

Anna Ijjas , Princeton University
[Host: Peter Arnold]
ABSTRACT:

In this talk, I will focus on cosmologies that replace the big bang with a big bounce. I will explain how, in these scenarios, the large-scale structure of the universe is determined during a contracting phase before the bounce and will describe the recent development of the first well-behaved classical (non-singular) cosmological bounce solutions.

SLIDESHOW:
Colloquium
Wednesday, February 1, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

 Available [Host: ] Colloquium Friday, January 27, 2017 3:30 PM Physics Building, Room 204  Add to your calendar

## "Searching for Dark Matter in Gravitational Waves"

Ilias Cholis , Johns Hopkins University
[Host: Peter Arnold]
ABSTRACT:

The nature of dark matter is one of the most longstanding and puzzling questions in physics. With cosmological measurements we have been able to measure its abundance with great precision. Yet, what dark matter is composed of remains a mystery.

In 2016 the first ever observation of gravitational waves from the coalescence event of two black holes was achieved by the LIGO interferometers.

Together with my collaborators we recently advocated that the interactions of 30 solar masses primordial black holes composing the dark matter could explain this event.

This opens up a new window in indirect searches for dark matter.

In my talk, I will discuss the various probes to distinguish between these mergers of primordial black holes, from the more traditional astrophysical black hole binaries.

One is through their mass spectrum, another is through cross-correlation of gravitational events with future overlapping galaxy catalogs. A third, is through their contribution to the stochastic gravitational wave background. Finally a fourth probe uses the fact that primordial black black holes form binaries with highly eccentric orbits. Those will then merge on timescales that in some cases are years, days or even minutes, retaining some eccentricity in the last seconds before the merger, which can be detected by LIGO and future ground based interferometers.

SLIDESHOW:
Colloquium
Wednesday, January 18, 2017
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Physics of Imperfect Graphene"

Eva Andrei , Rutgers University
[Host: Israel Klich ]
ABSTRACT:

Graphene in its pristine form has transformed our understanding of 2D electron systems leading to fundamental discoveries and to the promise of important applications. I will discuss new and surprising phenomena that emerge when the perfect honeycomb lattice of graphene is disrupted. In particular I will focus on the effects of single atom vacancies on graphene's electronic and magnetic properties as revealed by scanning tunneling microscopy and spectroscopy. These include charging the vacancy site into the supercritical regime where we observe the formation of an artificial 2D atom 1,  and electrostatically controlled Kondo screening of the vacancy magnetic moment.

1 J.Mao, Y.Jiang, D. Moldovan,  G. Li,  K. Watanabe, T. Taniguchi,   M. R. Masir, F.M. Peeters, E.Y. Andrei, Tunable Artificial Atom at a Supercritically Charged Vacancy in Graphene, Nature Physics 2016, doi:10.1038/nphys3665

Colloquium
Friday, December 2, 2016
3:30 PM
Physics Building, Room 203

## "Physics of the Dark Energy Survey (TBC)"

Marcelle Soares-Santos , Fermilab
[Host: Craig Group]
ABSTRACT:

DES is an ongoing imaging sky survey, the largest such survey to date. Its main science goal is to shed light onto dark energy by making precision measurements of the expansion history and growth of structure in the universe. In this talk I present an overview of our latest results and introduce a new DES initiative: searches for optical counterparts to gravitational wave events.

Colloquium
Friday, November 18, 2016
3:30 PM
Physics Building, Room 203

## "Available"

Colloquium
Friday, November 11, 2016
3:30 PM
Physics Building, Room 204

## "The Accelerating Universe"

Adam Reiss , Johns Hopkins University
[Host: Craig Group]
ABSTRACT:

A public lecture by Adam Reiss, recipient of the 2011 Nobel Prize for the detection of the accelerating expansion of the universe using distant supernovas.  The lecture will be presented at 7 pm on Wednesday, November 9, at the Paramount Theater on Charlottesville's Downtown Mall.

The  Physics  and  Astronomy  Departments  at  the  University  of Virginia in partnership the National Radio Astronomy Observatory invite the community to a special FREE public  lecture  by  Nobel  Laureate  Adam  Riess  at  The  Paramount  Theater  on  Wednesday,  November  9  at 7:00PM.    Prof.  Riess  will  speak  on  the  fascinating  topic  of  the  accelerating  universe.  Due  to  his  critical contributions, Prof. Riess shared the 2011 Nobel Prize "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae."  The term "supernovae" refers to stars exploding at the end of their lives. The team Prof. Riess worked with used a particular kind of supernova, called type Ia supernova,  to  understand  the  properties  of  distant  galaxies.    His  research  team  found  that  light  from distant  supernovae  was  weaker  than  expected  ‐  this  was  a  sign  that  the  expansion  of  the  Universe  was accelerating. Prof. Riess will discuss the excitement of this discovery, its implications, and current ongoing work to help answer remaining questions.

Colloquium
Wednesday, November 9, 2016
7:00 PM
The Paramount, Room The Auditorium

Special Nobel Lecture

## "Available"

Colloquium
Friday, November 4, 2016
3:30 PM
Physics Building, Room 204

## "Available"

Colloquium
Friday, October 28, 2016
3:30 PM
Physics Building, Room 204

## "Available"

Colloquium
Friday, October 21, 2016
3:30 PM
Physics Building, Room 204

## "Available"

Colloquium
Friday, October 14, 2016
3:30 PM
Physics Building, Room 204

## "Available"

Colloquium
Friday, October 7, 2016
3:30 PM
Physics Building, Room 204

## "Resolution of the black hole information paradox"

Samir Mathur , Ohio State
[Host: Peter Arnold]
ABSTRACT:

Some 40 years ago Hawking found a remarkable contradiction: if we accept the standard behavior of gravity in regions of low curvature, then the evolution of black holes will violate quantum mechanics. Resolving this paradox would require a basic change in our understanding of spacetime and/or quantum theory. This paradox has found an interesting resolution through string theory. While quantum gravity is normally expected to be important only at distances of order planck length, the situation changes when a large number N of particles are involved, as for instance in the situation where we make a large black hole. Then the length scale of quantum gravity effects grows with N, altering the black hole structure to a "fuzzball"; this effect resolves the paradox.

SLIDESHOW:
Colloquium
Friday, September 30, 2016
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Nuclear Weapons: Sources of Strength or Vulnerability? "

Aron Bernstein , MIT
[Host: Gordon Cates]
ABSTRACT:

An objective overview of the nuclear arms race will be presented with an emphasis  on the present situation. A brief sketch of how nuclear weapons work and some ironic lessons from history will be presented. Scientists' discussions about preventing proliferation and use started in the secrecy of the Manhattan Project and continued in public during the rapid cold war buildup to the present (e.g., Bulletin of the Atomic Scientists). The central role of the nuclear non-proliferation treaty, the Iran agreement, possible pathways to nuclear conflict, and a personal view of the outlook to prevent future nuclear weapons use, including the vital role of education, will be presented.

Aron Bernstein is Professor of Physics, Emeritus, MIT. His physics research has focused on experimental tests of the symmetries of the standard model (chiral anomaly and symmetry). He has followed the nuclear arms race carefully since the Cuban Missile Crisis, has taught courses on this subject, and has done research on arms control issues such as the dangers posed by the Russian and US short ballistic missile launch and warning times. He is a National Board Member of the Council for a Livable World, started by physicist Leo Szilard, which works with Congress on nuclear arms control issues.

Colloquium
Friday, September 23, 2016
3:30 PM
Physics Building, Room 204

 Graduate Town Hall Meeting Colloquium Friday, September 16, 2016 3:30 PM Physics Building, Room 204  Add to your calendar

## "Available"

Colloquium
Friday, September 9, 2016
3:30 PM
Physics Building, Room 204

## "Available"

Colloquium
Friday, September 2, 2016
3:30 PM
Physics Building, Room 204

## "Electron Circular Dichroism and the Origin of Life On Earth"

Tim Gay , University of Nebraska
[Host: Xiaochao Zheng]
ABSTRACT:

We have bombarded chiral halocamphor molecules in the gas phase with low-energy (< 1 eV), longitudinally-spin-polarized electrons, and investigated dissociative electron attachment (DEA) reactions:

e- + HA → H- + A,

where H is a halogen atom (Br or I) and A is the residual camphor fragment.  We observe that for a given target handedness, the total DEA cross section depends on the helicity of the incident electron.  In the case of iodocamphor at the lowest incident electron energies, this effect can be as large as two parts in 1000.  The observation of chiral sensitivity in a break-up reaction is important because, among other things, it validates the premise of the Vester-Ulbricht hypothesis regarding the origins of biological homochirality.  The sordid history of previous attempts to demonstrate such effects will be briefly reviewed.

SLIDESHOW:
Colloquium
Friday, August 26, 2016
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "The Remarkable Story of LIGO's Detection of Gravitational Waves"

Peter Shawhan , University of Maryland
[Host: Peter Arnold]
ABSTRACT:

On February 11, LIGO scientists announced the direct detection of gravitational waves, confirming a century-old prediction of Einstein's general theory of relativity.  This milestone was finally made possible with the incredibly sensitive Advanced LIGO detectors, combined with a certain measure of luck. This first event is already enough to investigate the properties of the source, test the theory of gravity, and project what more we can learn from future events.  I will share both the scientific meaning of the discovery and some of the personal stories behind it.

VIDEO:
Colloquium
Monday, May 2, 2016
3:30 PM
Physics Building, Room 203

Slideshow (PDF)

## "30 years of high Tc: Superfluid and normal-fluid densities in the cuprate superconductors"

David Tanner , University of Florida
[Host: Seunghun Lee]
ABSTRACT:

It was in April 1986 when Bednorz and Mueller of the IBM Zürich laboratories sent a paper about “possible high-Tc superconductivity” to Zeitschrift für Physik B.  The resulting bombshell changed condensed-matter physics forever.  Experimenters and theorists developed methods to measure and calculate in ways that were much improved over prior years. However, despite 30 years of intense study, the description of these materials remains incomplete. I’ll discuss the  discovery of the high Tc cuprates from the perspective of a participant.  I’ll then turn to what infrared spectroscopy can tell us about their properties. Measurements for a number of cuprate families of optical reflectance over a wide spectral range (far-infrared to ultraviolet) have been analyzed using Kramers-Kronig analysis to obtain the optical conductivity, s(w), and (by integration of the real part of the conductivity) the spectral weight of low- and mid-energy excitations. For the Kramers-Kronig analysis to give reliable results, accurate high-frequency extrapolations, based on x-ray atomic scattering functions, were used. When the optical conductivities of the normal and superconducting states are compared, a transfer of spectral weight from finite frequencies to the zero-frequency delta-function conductivity of the superconductor is seen. The strength of this delta function gives the superfluid density, rs. There are two ways to measure rs, using either the low energy spectral weight or by examination of the imaginary part, s2(w); both estimates show that 98% of the ab-plane superfluid density comes from low energy scales, below about 0.15 eV. Moreover, there is a notable difference between clean metallic superconductors and the cuprates.  In the former, the superfluid density is essentially equal to the conduction electron density. The cuprates, in contrast, have only about 20% of the ab-plane low-energy spectral weight in the superfluid. The rest remains in finite-frequency, midinfrared absorption. In underdoped materials the superfluid fraction is even smaller. The consequences of this observation for the electronic structure will be addressed.

SLIDESHOW:
Colloquium
Friday, April 29, 2016
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "How many electrons make a semiconductor nanocrystal film metallic? "

Boris Shklovskii , Univ. Minnesota
[Host: Eugene Kolomeisky]
ABSTRACT:

Films of semiconductor nanocrystals are used as a novel, low-cost electronic materials for optoelectronic devices. To achieve their full potential a better understanding of their conductivity as a function of concentration of donors is required. So far, it is not known how many donors will make a nanocrystal film metallic. In bulk semiconductors, the critical concentration of electrons at the metal-insulator transition is universally described by the famous Mott criterion. We show theoretically that in a dense NC film, where NCs touch each other by small facets with radius r << d, the critical concentration of electrons N at the metal-insulator transition satisfies the condition is given by N r^3 = 1.
This critical concentration is typically 100 times larger than the Mott one. In the accompanying experiments, we investigate the conduction mechanism in films of phosphorus-doped silicon nano-crystals. At the largest electron concentration achieved in our samples, which is half the predicted N, we find that the localization length of hopping electrons is close to three times the nano-crystals diameter, indicating that the film approaches the metal-insulator transition.

Colloquium
Friday, April 22, 2016
3:30 PM
Physics Building, Room 204

## "How to Understand Molecular Transport through Channels: The Role of Interactions"

Anatoly Kolomeisky , Rice University
[Host: Israel Klich ]
ABSTRACT:

The motion of molecules across channels and pores is critically important for understanding mechanisms of many biological, chemical, physical and industrial processes. Here we investigate the role of different types of interactions in the channel-facilitated molecular transport by analyzing exactly solvable discrete-state stochastic models. According to this approach, the channel transport is a non-equilibrium process that can be viewed as a set of coupled quasi-chemical transitions between discrete spatially separated states. It allows us to obtain a full dynamic description of the translocation via the pore, clarifying many aspects of these complex processes. We show that the strength and the spatial distribution of the molecule/channel interactions can strongly modify the particle fluxes through the system. Our analysis indicates that the most optimal transport is achieved when the binding sites are near the entrance or near the exit of the pore, depending on the sign of the interaction potentials. These observations allow us to explain current single-molecule experiments on the translocation of polypeptides through biological channels. We also suggest that the intermolecular interactions during the channel transport might significantly influence the overall translocation dynamics. Our explicit calculations show that the increase in the flux can be observed for some optimal interaction strengths. But the flux can also be fully suppressed for some conditions. The relevance of these results for biological systems is discussed. The physical-chemical mechanisms of these phenomena are analyzed from the microscopic point of view.

SLIDESHOW:
Colloquium
Friday, April 15, 2016
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Impact and Intrusion: the surprises and elegance of how nature arranges the texture of our lives"

Sidney R. Nagel , University of Chicago
[Host: Seunghun Lee]
ABSTRACT:

Many complex phenomena are so familiar that we hardly realize that they defy our normal intuition.  Examples include the anomalous flow of granular material, the long messy tendrils left by honey spooned from one dish to another, the pesky rings deposited by spilled coffee on a table after the liquid evaporates or the common splash of a drop of liquid onto a countertop.  Aside from being uncommonly beautiful to see, many of these phenomena involve non-linear behavior where the system is far from equilibrium.  Although most of the world we know is beyond description by equilibrium theories, we are still only at the threshold of learning how to deal with such deep and complex behavior.  Thus, these are phenomena that can lead the inquisitive into new realms of physics.

SLIDESHOW:
Colloquium
Thursday, April 14, 2016
7:00 PM
Chemistry Building, Room 402

Special Colloquium: Hoxton Lecture

Slideshow (PDF)

## "Seeds of Supermassive Black Holes at High Redshifts"

Isaac Shlosman , University of Kentucky
[Host: Eugene Kolomeisky]
ABSTRACT:

Detection of distant quasars at redshifts of ~6-7 provides a challenge to the standard picture of structure formation in the universe within the hierarchical framework, as the universe is less than a Gigayear old at this time. What are seeds of supermassive black holes (SMBHs) that power these luminous objects? After all,  massive objects should form late in the evolution ...  Did  SMBHs form as a result of stellar evolution? In my talk, I will address various aspects of this problem and discuss viable and emerging alternatives to this paradigm.

Colloquium
Friday, April 8, 2016
3:30 PM
Physics Building, Room 204

Joint Physics-Astronomy Colloquium

## "Do Electrons in a Metal Have the Same Charge as Free Electrons in Vacuum?"

Neil Zimmerman , NIST
[Host: Jongsoo Yoon]
ABSTRACT:

At NIST, we have the enjoyable jobs of combining i) state-of-the-art research with ii) the fascinating search for higher and higher accuracy measurements.  In this talk, I will i) introduce the SI system of units and explain why devices that can move around single electrons one-by-one are of great interest, ii) give an introduction to the nanoelectronic devices known as single electron transistors and pumps, iii) describe a high-accuracy measurements of the charge of electrons in a metal, and iv) discuss the possibility that this charge is not the same as the charge of a free electron in vacuum.

SLIDESHOW:
Colloquium
Friday, April 1, 2016
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Opportunities for Collaboration at Oak Ridge National Laboratory"

Ian Anderson , ORNL
[Host: Despina Louca]
Colloquium
Thursday, March 31, 2016
9:45 AM
Wilsdorf Hall, Room 200

## "Golden Era of Modern Magnetism "

Prof. Chia Ling Chien , Johns Hopkins University
[Host: Seunghun Lee]
ABSTRACT:

Magnetism has been an old subject dating back to antiquity.  Few could envision that modern magnetism would enter a golden era with the realization of so many new phenomena and game-changing technologies.  These remarkable advances are due to spin ½ of electrons, as illustrated in this talk through several recent examples, including pure spin current phenomena, skyrmion materials, and p-wave superconductivity.

Colloquium
Friday, March 25, 2016
3:30 PM
Physics Building, Room 204

## "Rediscovering Pluto: a panel on NASA's recent Pluto Mission (New Horizons)"

Alice Bowman and Anne Verbiscer
[Host: UVA Physics and Astronomy Departments]
ABSTRACT:

On July 14, 2015, New Horizons, an interplanetary space probe, flew by Pluto, capturing the first high resolution photographs of Pluto’s surface and atmosphere. New Horizons data has revealed stunning geology including ice volcanoes, Nitrogen ice glaciers, mysterious internal heating, and the “snakeskin” patterns among 50 other discoveries. UVA’s planetary astronomer, Anne Verbiscer, will describe Pluto’s amazing science phenomena, and Alice Bowman will explain the missions and engineering side of New Horizons sharing her experience as New Horizons’ MOM. This event is meant for the general public, and everyone is invited. A reception will follow the talk.

Sponsored by UVA Physics and Astronomy Departments.
Organized by Astronomical Society at UVA and SPS

A map showing the location of Maury Hall is available online at the following address:
http://www.virginia.edu/webmap/popPages/55-MauryHall.html

Colloquium
Thursday, March 24, 2016
7:30 PM
Maury Hall, Room 209

## "Atom Interferometry Measurements of Atomic Polarizabilities and Tune-out Wavelengths"

Alex Cronin , University of Arizona
[Host: Cass Sackett]
ABSTRACT:

Atom interferometry, in which de Broglie waves of matter are coherently split and later recombined to make interference fringes, is a precision measurement method with applications in many fields of physics.  In Arizona, we measured the ground-state static electric-dipole polarizabilities of Cs, Rb, and K atoms with 0.2% uncertainty using an atom beam interferometer.  We also measured a tune-out wavelength for K atoms with sub-picometer uncertainty.  I will discuss how these experiments use electric field gradients to induce polarizability-dependent phase shifts for atomic de Broglie waves. Our measurements provide benchmark tests for atomic structure calculations and thus test the underlying theory used to predict van der Waals forces and to interpret atomic parity non-conservation experiments.

SLIDESHOW:
Colloquium
Friday, March 18, 2016
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Physics Informed Machine Learning"

Michael Chertkov , LANL
[Host: Marija Vucelja]
ABSTRACT:

Machine Learning (statistical engineering) capabilities are in a phase of tremendous growth. Underlying these advances is a strong and deep connection to various aspects of statistical physics. There is also a great opportunity in pointing these tools toward physical modeling. In this colloquium I  illustrate the two-way flow of ideas between physics and statistical engineering on three examples from our team LANL. First, I review the work on  structure learning and statistical estimation in power system distribution (thus physical) networks. Then I describe recent progress in constructive understanding of graph learning (on example of inverse Ising model) illustrating that the generic inverse task (of learning) is computationally easy in spite of the fact that the direct problem (inference or sampling) is difficult. I conclude speculating how macro-scale models of physics (e.g. large eddy simulations of turbulence) can be learned from micro-scale simulations (e.g. of Navier-Stocks equations).

Colloquium
Friday, March 4, 2016
3:30 PM
Physics Building, Room 204

 Available Colloquium Friday, February 26, 2016 3:30 PM Physics Building, Room 204  Add to your calendar

## "Metamagnetism - its ubiquity and universality"

Bellave Shivaram , University of Virginia - Physics Dept.
[Host: Vittorio Celli]
ABSTRACT:

The emergent universality in the nonlinear magnetic response of itinerant metamagnets will be discussed. Recent experimental work on heavy fermions, Hunds metals, and single molecule magnets will be presented. The appeal of the ‘single energy scale model’ developed in the context of these new measurements [(a) "Universality in the Nonlinear Magnetic Response of Strongly Correlated Metals", B.S. Shivaram, D.G. Hinks, M.B. Maple and P. Kumar, Phys. Rev., B89, 241107(Rapid Communication), 2014. [b] "Metamagnetism and the Fifth Order Susceptibility in UPt3", B.S. Shivaram, Brian Dorsey, D.G. Hinks and Pradeep Kumar, Phys. Rev., B89, 161108(Rapid Communication), (2014). [c] “High Field Ultrasound Measurements in UPt3 and the Single Energy Scale Model of Metamagnetism”, B.S. Shivaram, V.W. Ulrich, P. Kumar and V. Celli, Phys. Rev.B, 91, 115110, 2015] will be critically examined.

Colloquium
Friday, February 19, 2016
3:30 PM
Physics Building, Room 204

## "Tailoring properties of single and bilayer layer transition metal dichalcogenides: looking beyond graphene*"

Talat Rahman , University of Central Florida
[Host: Vittorio Celli]
ABSTRACT:

Single-layer of molybdenum disulfide (MoS2) and other transition metal dichalcogenides appear to be promising materials for next generation nanoscale applications (optoelectronic and catalysis), because of their low-dimensionality, intrinsic direct band-gap which typically lies in the visible spectrum, and strikingly large binding energies for excitons and trions. Several experimental groups have already reported novel electronic and transport properties which place these material beyond graphene for device applications. MoS2 is also known to be a leading hydrodesulphurization catalyst. Efforts are underway to further tune these properties through alloying, defects, doping, coupling to a substrate, and formation of bilayer stacks (homo- and hetero-structures).  In this talk I will present results [1-3] which provide a framework for manipulating the functionality of these fascinating materials and take us closer to the goal of rational material design.  My emphasis will be on properties of pure and defect-laden single layer MoS2 with and without underlying support.  I will also provide rationale for the differences in the excitation energetics and ultrafast charge dynamics in single and bilayer (hetero and homo) dichalcogenides.

[1] D. Sun, et al., “An MoSx Structure with High Affinity for Adsorbate Interaction,” Angew. Chem. Int. Ed. 51, 10284 (2012).

[2] D. Le, T. B. Rawal, and T. S. Rahman, “Single-Layer MoS2 with Sulfur-Vacancies: Structure and Catalytic Application,” J. Phys. Chem. C 118, 5346 (2014).

[3] A. Ramirez-Torres, V.Turkowski, and T. S. Rahman, “Time-dependent density-matrix functional theory for trion excitations: application to monolayer MoS2,” Phys. Rev. B 90, 085419 (2014).

SLIDESHOW:
Colloquium
Friday, February 12, 2016
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "The Physics of Climate Change"

Michael Mann , Pennsylvania State Univ.
[Host: GPSA]
ABSTRACT:

I will review the basic underlying science of climate and climate change, including physically-based models of Earth's climate. I will motivate the use of a simple, zero-dimensional "Energy Balance Model" of Earth's radiative balance that can be used to estimate the global mean surface temperature of Earth. I will show how this model successfully reproduces the observed historical changes in global temperature, and how it can be used to assess various questions about future human-caused climate change.

VIDEO:
Colloquium
Friday, February 5, 2016
3:30 PM
Physics Building, Room 203

Slideshow (PDF)

## "Things that go bump in the data: QCD Puzzles, Predictions, and Prognoses"

Fred Olness , Southern Methodist University
[Host: Simonetta Liuti]
ABSTRACT:

The very successful Run I of the Large Hadron Collider (LHC) culminated in the discovery of the Higgs boson which was the subject of the 2013 Nobel Prize.

How will we know if there are other "undiscovered" particles in the data? (And, was there a hint from CERN last month???)  This will require improved calculations, and the key ingredients are:

i) higher-order theoretical cross section calculations, and

ii) precise Parton Distribution Functions (PDFs) that characterize the proton structure.

Surprisingly, these predictions are influenced by a wide range of data including precision low-energy nuclear results. Recent theoretical developments improve our ability to address the QCD multi-scale problem and higher orders across the full kinematic range.

We look at some of the topics, puzzles, and challenges that lie on the horizon, and identify areas where additional efforts are required.

SLIDESHOW:
Colloquium
Friday, January 29, 2016
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Building a quantum computer from the top down: massive-scale entanglement in the quantum optical frequency comb"

Olivier Pfister , UVA-Physics
[Host: Seunghun Lee]
ABSTRACT:

Quantum computing offers revolutionary promises of scientific and societal importance, based on its exponential speedup of particular tasks: on the one hand, Richard Feynman's quantum simulator would allow us to tackle currently intractable quantum chemistry problems (nitrogen fixation, carbon sequestration) as well as quantum physics ones (high-Tc superconductivity); on the other hand, Peter Shor's algorithm for factoring integers would render RSA encryption obsolete.

Building a practical quantum computer demands that one address the challenges of decoherence and scalability. While the platforms of trapped-ion qubits and of superconducting qubits have made spectacular progress in the fight against decoherence, our approach has been to tackle scalability, in particular by discovering a new “top down,” rather than “bottom up,” method for generating the entangled states, or "cluster" states, that enable the particular flavor of quantum computing called measurement-based, or one-way, quantum computing.

Our method uses the continuous variables of light — “qumodes,” rather than qubits — defined by the quadrature amplitudes of the quantized electromagnetic field emitted over the cavity modes, or quantum optical frequency comb, of a single optical parametric oscillator. We demonstrated a world-record cluster state size of 60 entangled qumodes (3 × 103 in progress), all simultaneously available in the frequency domain. I will also present our new proposal for generating cluster states of unlimited size by using both the time and frequency degrees of freedom.

Colloquium
Friday, January 22, 2016
3:30 PM
Physics Building, Room 204

Colloquium: Cancelled due to snow

## "Spatial Imaging of Quarks and Gluons in the Proton"

Charles Hyde , Old Dominion University
[Host: Simonetta Liuti]
ABSTRACT:

For many years, it was generally thought that spatial imaging of the proton was impossible in principle, due to the relativistic recoil of the proton when ever it is probed at momentum scales of order of the inverse of the proton size.  Two decades ago, a new set of QCD matrix elements were defined, called Generalized Parton Distributions (GPDs), that encode the spatial distributions of quarks and gluons transverse to a preferred momentum axis.  It was independently discovered that the GPDs are accessible experimentally in Deep Virtual Exclusive reactions:  high energy reactions of the type e p —> e p gamma.

I will review the progress of experimental efforts to measure GPDs, and discuss the extent to which spatial distributions can be extracted from present and future data.

SLIDESHOW:
Colloquium
Friday, December 4, 2015
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Discovery of Electron Neutrino Appearance from a Muon Neutrino Beam in T2K and Future Outlook for Discovery of CP Violation in Lepton Sector in DUNE at LBNF"

Chang Kee Jung , SUNY at Stony Brook
[Host: Seunghun Lee]
ABSTRACT:

Matter-antimatter asymmetry is one of the most outstanding mysteries of the universe that provides a necessary condition to our own existence. There have been various attempts to solve this mystery including 'Baryogenesis' hypothesis. However, the B-factory experiments during the last decade showed that the observed CP-violation (CPV) in the quark sector is not big enough for baryogenesis to be a viable solution to the matter-antimatter asymmetry. This leads us to the 'Leptogenesis' hypothesis, in which CPV in the lepton section plays a crtical role to create the matter-antimater asymmetry at the onset of the Big Bang. Thus, experimental observation of CPV in the lepton sector could prove to be tantamount to one of the most important discoveries in our understanding of the universe.

In 2011, the T2K experiment published a result that provided the first indication for a non-zero $\theta_{13}$, the last unknown mixing angle in the lepton sector at that time, at 2.5 sigma level of significance. In 2013, after analyzing two more years of data taken since 2011, the experiment reported "Observation of electron neutrino appearance from a muon neutrino beam" at 7.3 sigma level of significance. While neutrino oscillation has been well-established since the discovery by the Super-Kamiokande experiment in 1998, there have not been a definitive observation of neutrino oscillation in a so-called "appearance mode", and this new T2K observation is the first time an explicit neutrino flavor (electron) appearance is observed from another neutrino flavor (muon). This observation also opens the door to study CPV in neutrinos. When incorporating recent precision measurements on $\theta_{13}$ by the reactor experiments along with other neutrino oscillation parameter measurements, T2K data show an intriguing initial result on the $\delta_{CP}$, which is further corroborated by the Super-Kamiokande atmospheric neutrino results as well as the most recent results from NOvA.

Ultimately, however, in order to establish unequivocal results on leptonic CPV, we need a next generation experiment with a more powerful beam, and a larger and/or higher resolution detector. The Deep Underground Neutrino Experiment (DUNE) in US that is newly established as a truly international collaboration, is such an experiment. Physics goals of DUNE include: discovery of CPV in the lepton sector, detrmination of mass hierarchy, discovery of proton decay and observation of neutrinos from the Type-II supernovae. In this talk I will introduce the rapidly developing DUNE experiment and the collaboration, and also discuss possible opportunities for participation.

I will also briefly comment on the Nobel Prize in Physics 2015 as well as The Breakthrough Prize in Fundamental Physics 2016 that were given to the
neutrino oscillation experiments.

Colloquium
Friday, November 20, 2015
3:30 PM
Physics Building, Room 204

## "Friction, magnetism and superconductivity: Are they interrelated?"

Jackie Krim , North Carolina State University
[Host: Joe Poon]
ABSTRACT:

Studies of the fundamental origins of friction have undergone rapid progress in recent years with the development of new experimental and computational techniques for measuring and simulating friction at atomic length and time scales.  The increased interest has sparked a variety of discussions and debates concerning the nature of the atomic-scale and quantum mechanisms that dominate the dissipative process by which mechanical energy is transformed into heat.  Measurements of the sliding friction of physisorbed monolayers and bilayers in gaseous and liquid enviroments provide information on the relative contributions of electronic, magnetic, electrostatic and phononic dissipative mechanisms. The experiments will be discussed within the context of current theories of how friction originates at the atomic scale.

SLIDESHOW:
Colloquium
Friday, November 13, 2015
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, November 6, 2015 3:30 PM Physics Building, Room 204  Add to your calendar

## "A âRoughâ View of Friction and Adhesion"

Mark Robbins , Johns Hopkins University
[Host: Seunghun Lee]
ABSTRACT:

Friction affects many aspects of everyday life and has played a central role in technology dating from the creation of fire by rubbing sticks together to current efforts to make nanodevices with moving parts. The friction "laws" we teach today date from empirical relationships observed by da Vinci and Amontons centuries ago. However, understanding the microscopic origins of these laws remains a challenge. While Amontons said area was proportional to load and independent of area, most modern treatments assume that friction is proportional to the real area of contact where atoms on opposing surfaces are close enough to repel. Calculating this area is complicated because elastic interactions are long range and surfaces are rough on a wide range of scales. In many cases they can be described as self-affine fractals from nanometer to millimeter scales. The talk will first show that this complex problem has a simple solution. Dimensional analysis implies a linear relation between real contact area and load that can explain both Amontons' laws and many exceptions to them. Next the talk will explain why we can't climb walls like spiderman even though the attractive interactions between atoms on our finger tips should provide enough force to support our weight. The talk will conclude by considering how forces in the contact area give rise to friction. Friction shows surprisingly counterintuitive and complex behavior in nanometer to micrometer scale contacts and only a few explanations are consistent with macroscopic measurements.

Colloquium
Friday, October 30, 2015
3:30 PM
Physics Building, Room 204

## "Broadband Molecular Rotational Spectroscopy for Chemical Dynamics and Molecular Structure"

Brooks Pate , UVA - Chemistry
[Host: Thomas Gallagher]
ABSTRACT:

Until about 2005, molecular rotational spectroscopy was performed using narrowband (~1 MHz) excitation of a low-pressure gas in a resonant cavity.  This method offers high sensitivity for each data acquisition, but the time required to perform a spectrum scan over about 10 GHz, needed to capture the rotational spectrum, was a major limitation to applications of the technique.  Advances in high-speed digital electronics have made it possible to design spectrometers that offer instantaneous, broadband (> 10 GHz) performance.  During our initial work with high-speed arbitrary waveform generators and digitizers (with Tom Gallagher) we developed the method of chirped pulse Fourier transform rotational spectroscopy that uses a pulse with linear chirp to phase-reproducibly excite the gas sample.  The subsequent coherent emission (free induction decay) is detected with the high-speed digitizer and the frequency domain spectrum is obtained using FFT analysis.  Since the introduction of the technique in 2008 [1], the method has been applied to unimolecular reaction dynamics [2], the structures of molecular clusters [3], and the laboratory identification of molecules in the interstellar medium [4].  The technique has been extended to mm-wave spectroscopy with applications to Rydberg spectroscopy [5], chemical reaction dynamics, and analytical chemistry.  The broadband technique has also enabled a new generation of molecular structure studies in the field of chirality [6] with the potential for solving significant challenges for real-time pharmaceutical manufacturing.

References

[1] G.G. Brown, B.C. Dian, K.O. Douglass, S.M. Geyer, and B.H. Pate, “A Broadband Fourier Transform Microwave Spectrometer Based on Chirped Pulse Excitation” Rev. Sci. Instrum. 79, 053103 (2008).

[2] B.C. Dian, G.G. Brown, K.O. Douglass, and B.H. Pate, “Measuring Picosecond Isomerization Dynamics via Ultra-broadband Fourier Transform Microwave Spectroscopy”, Science 320, 924-928 (2008).

[3] C. Pérez, M.T. Muckle, D.P. Zaleski, N.A. Seifert, B. Temelso, G.C. Shields, Z. Kisiel, and B.H. Pate, “Structures of Cage, Prism, and Book Isomers of Water Hexamer from Broadband Rotational Spectroscopy”, Science 336, 897-901 (2012).

[4] D.P. Zaleski, N.A. Seifert, A.L. Steber, M.T. Muckle, R.A. Loomis, J.F. Corby, O. Martinez, Jr., K.N. Crabtree, P.R. Jewell, J.M. Hollis, F.J. Lovas, D. Vasquez, J. Nyiramahirwe, N.  Sciortino, K. Johnson, M.C. McCarthy, A.J. Remijan, and B.H. Pate, “Detection of E-cyanomethanimine towards Sagittarius B2(N) in the Green Bank Telescope PRIMOS Survey”, Ap. J. Letters, 765, L10 (2013).

[5] K. Prozument, A.P. Colombo, Y. Zhou, G.B. Park, V.S. Petrovic, S.L. Coy, and R.W. Field, “Chirped-pulse Millimeter-wave Spectroscopy of Rydberg-Rydberg Transitions”, Phys. Rev. Lett. 107, 143001 (2011).

[6] D. Patterson, M. Schnell, and J.M. Doyle, “Enantiomer-specific detection of chiral molecules via microwave spectroscopy”, Nature 497, 475 (2013).

SLIDESHOW:
Colloquium
Friday, October 23, 2015
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Surfing on a Plasma Wave - Can a Grand Challenge for Engineering Answer the Big Questions of Physics?"

Thomas Katsouleas , Provost and Department of Physics UVA
[Host: Joseph Poon]
ABSTRACT:

The National Academy of Engineering has identified 14 Grand Challenges for Engineering for the 21st Century, spanning human needs from sustainability to security, health and joy of living.  The last category includes such topics as engineering the tools of scientific discovery. This talk will include a brief review of the NAE Grand Challenges and the response of higher education to the Challenges, and will conclude with a review of one Grand Challenge topic:  the development of ultra-compact particle accelerators based on surfing at (nearly) the speed of light on waves created by lasers or particle beams in a plasma gas. The prospects of these devices as tools of scientific discovery as well as beam therapy will be discussed.

VIDEO:
Colloquium
Friday, October 16, 2015
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, October 9, 2015 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, October 2, 2015 3:30 PM Physics Building, Room 204  Add to your calendar

## "Iron Chef: recipes for building magnetic structures atom by atom"

[Host: Israel Klich ]
ABSTRACT:

Understanding Magnetism is a complex undertaking: it relies on our knowledge of the exact position of magnetic ions in a crystal and their interactions. More important, at its core, this is fundamentally a quantum problem and requires understanding the cooperative effects of many degrees of freedom. In the past decade, we have witnessed enormous progress in experiments that consist of placing magnetic atoms at predetermined positions on substrates, and building magnetic nanostructures, one atom at a time. The electrons in the substrate mediate the interactions between the spins, and scanning tunneling microscopy allows one to study their properties.

In order to understand these interactions, we rely on a theory developed decades ago by Ruderman, Kittel, Kasuya, and Yosida, dubbed "RKKY Theory", which applies when the spins are classical. The quantum nature of the electronic spin introduces more complexity, and competition with another quantum phenomena: the Kondo effect. The combined effect is non-trivial, and can only be studied by numerical means.  I will describe this effect by introducing an exact mapping onto an effective one-dimensional problem that we can solve with the density matrix renormalization group method (DMRG). I will also show that for dimension d>1, Kondo physics dominates even at short distances, while the ferromagnetic RKKY state is energetically unfavorable. This may have important implications for our understanding of heavy fermion materials and magnetic semiconductors.

SLIDESHOW:
Colloquium
Friday, September 25, 2015
3:15 PM
Physics Building, Room 204

Slideshow (PDF)

## "Hoos at Fermilab"

Craig Group , University of Virginia
[Host: Joe Poon]
ABSTRACT:

I will review the current status of the Mu2e and NOvA experiments at Fermilab.  These experiments hope to shed light on several important topics in particle physics:  neutrino oscillations, lepton flavor, the matter/antimatter asymmetry of the Universe, dark matter, and others.   As I describe the status and goals of these experiments I will highlight the impact of our UVA efforts.

Colloquium
Friday, September 18, 2015
3:30 PM
Physics Building, Room 204

## "Love triangles, quantum fluctuations and spin jam "

Seung-Hun Lee , UVA-Physics
[Host: Joe Poon]
ABSTRACT:

When magnetic moments are interacting with each other in a situation resembling that of complex love triangles, called frustration, a large set of states that are energetically equivalent emerge. This leads to exotic spin states such as spin liquid and spin ice. In their paper recently published in the Proceedings of the National Academy of Sciences (PNAS), we presented evidence for the existence of a topological glassy state, that we call a spin jam, induced by quantum fluctuations. The case in point is SrCr9pGa12-9pO19 (SCGO(p)), a highly frustrated magnet, in which the magnetic Cr ions form a quasi-two-dimensional triangular system of bi-pyramids. This system has been an archetype in search for exotic spin states. Understanding the nature of the state has been a great intellectual challenge. Our new experimental data and theoretical spin jam model provide for the first time a coherent understanding of the phenomenon. Furthermore, the findings strongly support the possible existence of purely topological glassy states.

Colloquium
Friday, September 11, 2015
3:30 PM
Physics Building, Room 204

## "The Novel World of Hadron Physics"

Stanley J. Brodsky , SLAC, Stanford University
[Host: Dinko Pocanic]
ABSTRACT:

I will survey a number of exciting new developments in hadron physics.

These include: new insights into the nature of the color-confi ning con finement quark potential in quantum chromodynamics; a novel application of supersymmetry to hadron physics; the relation between the parameter ΛMS` which controls high-energy interactions of quarks to the mass of the proton; and the elimination of the renormalization scale ambiguity for perturbative QCD calculations.

I will also discuss several novel experimental tests of QCD which can be performed at JLab, including: hard exclusive and diff ractive reactions, flavor-dependent antishadowing of nuclear interactions; intrinsic strange- and charm-quark phenomena; the production of tetraquarks and other exotic hadronic states; and factorization-breaking lensing phenomena.

SLIDESHOW:
Colloquium
Monday, April 27, 2015
3:30 PM
Physics Building, Room 203

Special Colloquium: INPP Annual Lecture

Slideshow (PDF)

## "Ultracold molecules â a new frontier for quantum physics and chemistry"

Jun Ye , JILA, National Institute of Standards and Technology, University of Colorado
[Host: Olivier Pfister]
ABSTRACT:

Molecules cooled to ultralow temperatures provide fundamental new insights to strongly correlated quantum systems, molecular interactions and chemistry in the quantum regime, and precision measurement.  Complete control of molecular interactions by producing a molecular gas at very low entropy and near absolute zero has long been hindered by their complex energy level structure. Recently, a range of scientific tools have been developed to enable the production of molecules in the quantum regime. Here, molecular collisions follow full quantum descriptions.  Chemical reaction is controlled via quantum statistics of the molecules, along with dipolar effects. Further, molecules can be confined in reduced spatial dimensions and their interactions precisely manipulated via external electromagnetic fields.  For example, by encoding a spin-1/2 system in rotational states, we realize a spin lattice system where many-body spin dynamics are directly controlled by long-range and anisotropic dipolar interactions. These new capabilities promise further explorations of strongly interacting and collective quantum effects in exotic quantum matter.

SLIDESHOW:
Colloquium
Friday, April 24, 2015
3:30 PM
Physics Building, Room 204

OSA & SPIE joint Student Chapter at UVA

Slideshow (PDF)

 Available Colloquium Friday, April 17, 2015 3:30 PM Physics Building, Room 204  Add to your calendar
 Boris Shklovskii , University of Minnesota [Host: E. Kolomeisky] Colloquium Wednesday, April 15, 2015 3:30 PM Physics Building, Room 204  Add to your calendar

## "Inflationary Cosmology: Is Our Universe Part of a Multiverse?"

Alan Guth , MIT
ABSTRACT:

Inflationary cosmology gives a plausible explanation for many observed features of the universe, including its uniformity, its mass density, and the patterns of the ripples that are observed in the cosmic microwave background. Beyond what we can observe, most versions of inflation imply that our universe is not unique, but is part of a possibly infinite multiverse. I will describe the workings of inflation, the evidence for inflation, and why I believe that the possibility of a multiverse should be taken seriously.

SLIDESHOW:
Colloquium
Wednesday, April 15, 2015
7:00 PM
Chemistry Building, Room Chemistry Building, Room 402

Special Colloquium: Hoxton Lecture

Slideshow (PDF)

## "Engaging with DPRK for Science Diplomacy and World Peace"

ChanMo Park , Chancellor of PUST/Former President of POSTECH
[Host: Seunghun Lee]
ABSTRACT:

As Chancellor of the Pyongyang University of Science & Technology (PUST) starting in October, 2010, I have seen the slow changes in DPRK, especially after Kim Jong Un took over the power in January, 2012. Globalizing DPRK is essential for peaceful coexistence and eventual reunification of two Koreas. One way to achieve this goal is Science Diplomacy, in particular educating young talents and globalizing them.

In this colloquium, a brief introduction about collaborative activities in science and technology between South and North Koreas will be presented, followed by more extensive presentation about the history and current status of PUST. And then the globalization efforts of PUST will be presented, to show that the PUST students are being internationalized and it is hoped that they will globalize their country in the near future, which will make an important contribution to the World Peace.

Colloquium
Friday, April 10, 2015
3:30 PM
Physics Building, Room 204

## "Discovering Ultra-High Energy Cosmic Rays with your Smartphone"

Mike Mulhearn , UC Davis
[Host: Bob Hirosky]
ABSTRACT:

Cosmic rays which encounter the Earth's atmosphere produce showers of muons and high-energy photons, which can be detected using a smartphone camera. The CRAYFIS experiment was devised to observe cosmic rays at ultra-high energy (UHE) using the existing network of smartphones as a ground detector array. We'll describe our custom app, our lab measurements of smartphone efficiency, and our latest projections for the sensitivity of the CRAYFIS array to UHE cosmic rays.

Colloquium
Friday, April 3, 2015
3:30 PM
Physics Building, Room 204

## "A new way to image: MRI with a 10,000,000-fold increase in sensitivity"

Gordon Cates , University of Virginia
[Host: Dinko Pocanic]
Colloquium
Friday, March 27, 2015
3:30 PM
Physics Building, Room 204

## "Screening of charge and structural motifs in oxides"

Peter Littlewood , Argonne National Laboratory and University of Chicago
[Host: Despina Louca]
ABSTRACT:

The boundary between metal and insulator remains a fruitful source of emergent phenomena in materials, ranging from oxides, to cold atoms. Typically the insulating side of this boundary is occupied by an electronic crystal (though often disordered), and at higher temperatures a polaronic liquid or bad metal. While the paradigm Hamiltonian for this transition involves only short –range electronic correlations, in practice the transition is tuned by disorder, by screening of longer range Coulomb forces, and by coupling to the lattice.  These lectures will discuss a few of these phenomena in real oxide systems including bulk and interface transition metal oxides.

Heterostructure oxides offer the opportunity to build in electric fields by precise control of chemistry on the atomic scale, used recently to generate modulation doping of two- dimensional electron gases (2DEG) in oxides. The origin of the 2DEG, whether in pristine or defected materials, is under debate. I will discuss the role of surface redox reactions, in particular O vacancies, as the source of mobile carriers, and also discuss their role in the switching of ferroelectricity in ultra-thin films.

While electric charges can be screened by mobile carriers, the same is not true of strain fields, which have intrinsic long-range interactions that cannot be screened. When strain fields are produced as a secondary order parameter in phase transitions - as for example in ferroelectrics - this produces unexpected consequences for the dynamics of order parameter fluctuations, including the generation of a gap in what would otherwise have been expected to be Goldstone modes. In some cases, eg manganites and nickelates, other intra-cell modes can nonlinearly screen the order parameter, which produces a strong sensitivity of ordering to octahedral rotations, essentially a jamming transition. This is relevant for tuning entropic effects at phase transitions, perhaps to enhance electro-caloric effects.

Colloquium
Friday, March 20, 2015
3:30 PM
Physics Building, Room 204

 Available Colloquium Friday, March 6, 2015 3:30 PM Physics Building, Room 204  Add to your calendar

## "Quantum-gas physics in orbit: prospects for microgravity Bose-Einstein condensates aboard NASA's Cold Atom Laboratory"

[Host: Cass Sackett]
ABSTRACT:

Notions of geometry, topology, and dimensionality have directed the historical development of quantum-gas physics, as has a relentless search for longer-lived matter-wave coherence and lower absolute temperature. With a toolbox of forces for confinement, guiding, and excitation, physicists have used quantum gases to test fundamental ideas in quantum theory, statistical mechanics, and in recent years notions of strongly-correlated many-body physics from the condensed-matter world.  Some of this work has been hampered by terrestrial gravity; levitation schemes of varying degree of sophistication are available, as are atomic-fountain and drop-tower microgravity facilities, but the long-term free-fall environment of low-Earth orbit remains a tantalizing location for quantum-gas experiments.

I will review a planned NASA microgravity program set to launch to the International Space Station in 2016. One set of experiments will explore a trapping geometry for quantum gases that is both theoretically compelling and difficult to attain terrestrially: that of a spherical or ellipsoidal shell. This trap could confine a Bose-Einstein condensate to the surface of an experimentally-controlled “bubble.” Other experiments will focus on atom interferometry and few-body physics. I will also review recent terrestrial work tailoring periodic geometries for BEC toward interesting solid-state analogues.

SLIDESHOW:
Colloquium
Friday, February 27, 2015
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Thursday, February 26, 2015 3:30 PM Physics Building, Room 204  Add to your calendar

## "From correlated topological insulators to iridates and spin liquids"

Stephan Rachel , Dresden University of Technology
[Host: Joe Poon]
ABSTRACT:

The non-interacting topological insulators (TIs) have attracted great interest in the last decade. While this class of materials is today well-understood, the effect of electron-eletron interactions in such systems remains in general elusive. In this talk, I will address two different aspects of interactions in 2D topological band structures: (i) in some cases, strongly interacting TI models can be used to describe the exotic magnetic properties of certain transition metal oxides. (ii) in other cases, strong interactions can drive a TI into spin-liquid phases.

Colloquium
Wednesday, February 25, 2015
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Inflation, Dark Matter, and Gravity Waves"

Qaisar Shafi , Bartol Institute, University of Delaware
[Host: PQ Hung]
ABSTRACT:

The Standard Model of strong and electroweak interactions, together with Einstein's theory of general relativity, provide the basis for the highly successful hot big bang cosmology. A large quantity of groundbreaking cosmological observations favor an epoch of primordial inflation, during which the very early universe experienced an exponentially rapid expansion phase before transitioning to a hot, radiation dominated ('big bang') phase. The present universe, it is now widely accepted, is largely dominated by dark energy, whose nature is entirely mysterious, and also by dark matter, presumably consisting of some relic and still undetected elementary particle.

Some aspects of inflationary cosmology will be reviewed, including its prediction concerning the existence of primordial gravity waves whose discovery would have profound implications for high energy physics and cosmology.

SLIDESHOW:
Colloquium
Friday, February 20, 2015
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Uncovering the Fibonacci Phase in Z3 Parafermion Systems"

Miles Stoudenmire , Perimeter Institute
[Host: Joe Poon]
ABSTRACT:

Recently there has been great progress in realizing platforms for topological quantum computation, with mounting evidence of the experimental observation of Majorana zero modes. However, braiding such zero modes does not yield a set of transformations sufficient to perform universal, fault tolerant computation. One way forward is to engineer systems realizing Z3 parafermion zero modes, which generalize Majorana zero modes. Coupled Z3 parafermions could hybridize into a phase supporting bulk Fibonacci anyons, a type of non-Abelian anyon that does have universal braiding statistics.

Using the density matrix renormalization group (DMRG), we study a two-dimensional model of coupled Z3 parafermions. By working close to the weakly-coupled chain limit, we are able to identify the Fibonacci phase on cylinders as small as four sites in circumference then track its evolution, finding it survives even to the isotropic limit of our model on larger cylinders. We examine the extent of this phase and the wider phase diagram of our model, which turns out to harbor a second topological phase.

SLIDESHOW:
Colloquium
Thursday, February 19, 2015
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "First-principles studies of oxide surfaces and interfaces"

Andrei Malashevich , Yale University
[Host: Joe Poon]
ABSTRACT:

Quantum-mechanical calculations based on methods that do not require any empirical input (first-principles calculations) have become an indispensable tool in studies of materials properties. In this talk, I will focus on applications of first-principles methods to studies of perovskite oxide surfaces and interfaces. Depending on the choice of cations, oxides can have almost any desired property. I will present two examples of materials that exhibit relation between structure and electronic properties at surfaces and interfaces. First, I will discuss an interface between metallic LaNiO3 thin film and ferroelectric PbTiO3. The polar field created by a ferroelectric can be used to modulate the conductivity of a channel material. This allows one to design non-volatile electronic devices based on the ferroelectric field effect. Typically, in the ferroelectric field effect, switching the polar state of a ferroelectric changes the carrier density in the channel material. I will show that in the LaNiO3/PbTiO3 interface the conductivity of the interface changes due to changes in carrier mobility, which in turn is related to structural distortions at the interface and appearance of two-dimensional conductivity in PbTiO3 at the interface. Second, I will present a study of properties of the (001) surfaces of thin LaNiO3 films. These films show dramatic differences in conductivity depending on the surface termination (LaO vs NiO2). We find that in this case, the conductivity is related to the polar structural distortions appearing at the surfaces of films.

Colloquium
Friday, February 13, 2015
3:30 PM
Physics Building, Room 204

## "Phase incoherence driven melting of order parameters in cuprate high temperature superconductors and disordered charge density wave systems"

Utpal Chatterjee , University of Virginia
[Host: Joe Poon]
ABSTRACT:

Charge density waves (CDWs) and superconductivity are canonical examples of symmetry breaking in materials. Both are characterized by a complex order parameter – namely an amplitude and a phase. In the limit of weak coupling and in the absence of disorder, the formation of pairs (electron-electron for superconductivity, electron-hole for CDWs) and the establishment of macroscopic phase coherence both occur at the transition temperature Tc that marks the onset of long-range order. But, the situation may be different at strong coupling or in the presence of disorder. We have performed extensive experimental investigations on pristine and intercalated samples of 2H-NbSe2, a CDW material with strong electron-phonon coupling, using a combination of structural (X-ray), spectroscopic (photoemission and tunnelling) and transport probes. We find that Tc(δ) is suppressed as a function of the concentration (δ) of the intercalated atoms and eventually vanishes at a critical value of δ=δc leading to quantum phase transition (QPT). Our integrated approach provides clear signatures that the phase of the order parameter becomes incoherent at the quantum/ thermal phase transition, although the amplitude remains finite over an extensive region above Tc and beyond δc. This leads to the persistence of an energy gap in the electronic spectra even though there is no long-range order, a phenomenon strikingly similar to the so-called pseudogap in completely different systems such as high temperature superconductors, disordered superconducting thin films and cold atoms.

Colloquium
Monday, February 9, 2015
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Stiffness from disorder in frustrated quasi-two-dimensional magnets"

Gia-Wei Chern , Los Alamos National Lab
[Host: Joe Poon]
ABSTRACT:

Frustrated magnetism has become an extremely active field of research. The concept of geometrical frustration dates back to Wannier’s 1950 study of Ising antiferromagnet on the triangular lattice. This simple system illustrates many defining characteristics of a highly frustrated magnet, including a macroscopic ground-state degeneracy and the appearance of power-law correlations without criticality. In this talk I will discuss a simple generalization of the triangular Ising model, namely, a finite number of vertically stacked triangular layers. Our extensive numerical simulations reveal a low temperature reentrance of two Berezinskii-Kosterlitz-Thouless transitions. In particular, I will discuss how short-distance spin-spin correlations can be enhanced by thermal fluctuations, a phenomenon we termed stiffness from disorder. This is a generalization of the well-known order-by-disorder mechanism in frustrated magnets. I will also present an effective field theory that quantitatively describes the low-temperature physics of the multilayer triangular Ising antiferromagnet.

Colloquium
Friday, February 6, 2015
3:30 PM
Physics Building, Room 204

 Available Colloquium Friday, January 30, 2015 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Thursday, January 29, 2015 3:30 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, January 23, 2015 3:30 PM Physics Building, Room 204  Add to your calendar

## "Jamming and the Anticrystal"

Andrea Liu , University of Pennsylvania
[Host: Seunghun Lee & Israel Klich]
ABSTRACT:

When we first learn the physics of solids, we are taught the theory of perfect crystals. Only later do we learn that in the real world, all solids are imperfect. The perfect crystal is invaluable because we can describe real solids by perturbing around this extreme limit by adding defects. But such an approach fails to describe a glass, another ubiquitous form of rigid matter. I will argue that the jammed solid is an extreme limit that is the anticrystal--an opposite pole to perfect order. Like the perfect crystal, it is an abstraction that can be understood in depth and used as a starting point for understanding the mechanical properties of solids with surprisingly high amounts of order. Unlike the crystal, it is also a starting point for developing mechanical metamaterials whose Poisson ratios can be tuned anywhere from the completely incompressible to the completely auxetic limit.

SLIDESHOW:
Colloquium
Friday, January 16, 2015
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Massless and Massive Electrons: Relativistic Physics in Condensed Matter Systems"

Vidya Madhavan , University of Illinois at Urbana-Champaign
[Host: Jeffrey Teo]
ABSTRACT:

Electrons in free space have a well-defined mass. Recently, a new class of materials called topological insulators were discovered, where the low energy electrons have zero mass. In fact, these electrons can be described by the same massless Dirac equation that is used to describe relativistic particles travelling close to the speed of light. In this talk I will describe our recent experimental and theoretical investigations of a class of materials called Topological Crystalline Insulators (TCIs) [1]. TCIs are recently discovered materials [2,3] where topology and crystal symmetry intertwine to create linearly dispersing Fermions similar to graphene. To study this material we used a scanning tunneling microscope [3,4,5]. With the help of our high-resolution data, I will show how zero-mass electrons and massive electrons can coexist in the same material. I will discuss the conditions to obtain these zero mass electrons as well the method to impart a controllable mass to the particles and show how our studies create a path to engineering the Dirac band gap and realizing interaction-driven topological quantum phenomena in TCIs.

[1] L. Fu, Topological Crystalline Insulators. Phys. Rev. Lett. 106, 106802 (2011).

[2] T. H. Hsieh et al., Topological crystalline insulators in the SnTe material class. Nat.Commun. 3, 982 (2012).

[3] Y. Okada, et al., Observation of Dirac node formation and mass acquisition in a topological crystalline insulator, Science 341, 1496-1499 (2013)

[4] Ilija Zeljkovic, et al., Mapping the unconventional orbital texture in topological crystalline insulators, Nature Physics 10, 572–577 (2014)

[5] Ilija Zeljkovic, et al., Dirac mass generation from crystal symmetry breaking on the surfaces of topological crystalline insulators, arXiv:1403.4906

SLIDESHOW:
Colloquium
Friday, December 5, 2014
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Twists in quantum magnets"

David Alan Tennant , Spallation Neutron Source, Oak Ridge National Laboratory
[Host: Seunghun Lee]
ABSTRACT:

Neutrons provide the ability to look at quantum states of matter in unrivaled detail. Using quantum magnets in conjunction with magnetic fields exotic phases of matter can be generated that are highly quantum entangled. The wave functions in these states can be probed in space and time and in quantum critical states in particular elaborate symmetries and strange properties like fractional quantum numbers are revealed. In this talk I will show some of the remarkable physics that can be explored and how neutron scattering can be used to investigate what is going on.

SLIDESHOW:
Colloquium
Friday, November 21, 2014
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Screening of charge and structural motifs in oxides"

CANCELED Peter Littlewood , Argonne National Laboratory
[Host: Despina Louca]
ABSTRACT:

The boundary between metal and insulator remains a fruitful source of emergent phenomena in materials, ranging from oxides, to cold atoms. Typically the insulating side of this boundary is occupied by an electronic crystal (though often disordered), and at higher temperatures a polaronic liquid or bad metal. While the paradigm Hamiltonian for this transition involves only short –range electronic correlations, in practice the transition is tuned by disorder, by screening of longer range Coulomb forces, and by coupling to the lattice.  These lectures will discuss a few of these phenomena in real oxide systems including bulk and interface transition metal oxides.

Heterostructure oxides offer the opportunity to build in electric fields by precise control of chemistry on the atomic scale, used recently to generate modulation doping of two- dimensional electron gases (2DEG) in oxides. The origin of the 2DEG, whether in pristine or defected materials, is under debate. I will discuss the role of surface redox reactions, in particular O vacancies, as the source of mobile carriers, and also discuss their role in the switching of ferroelectricity in ultra-thin films.

While electric charges can be screened by mobile carriers, the same is not true of strain fields, which have intrinsic long-range interactions that cannot be screened. When strain fields are produced as a secondary order parameter in phase transitions - as for example in ferroelectrics - this produces unexpected consequences for the dynamics of order parameter fluctuations, including the generation of a gap in what would otherwise have been expected to be Goldstone modes. In some cases, eg manganites and nickelates, other intra-cell modes can nonlinearly screen the order parameter, which produces a strong sensitivity of ordering to octahedral rotations, essentially a jamming transition. This is relevant for tuning entropic effects at phase transitions, perhaps to enhance electro-caloric effects.

Colloquium
Friday, November 14, 2014
3:30 PM
Physics Building, Room 204

## "Leptogenesis"

Yuval Grossman , Cornell University
[Host: Bob Hirosky]
ABSTRACT:

There are three open questions in physics which seem unrelated: Why is there only matter around us? How neutrinos acquire their tiny masses? Why all the particles in Nature have integer electric charge? It turns out that these open questions may be related. In this talk I will explain the questions, the connection between them and describe the on-going theoretical and experimental efforts in understanding them.

SLIDESHOW:
Colloquium
Friday, November 7, 2014
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Hoping to get something out of nothing: Vacuum fluctuations and Newtonian (?) gravity"

Ricardo Decca , IUPUI
[Host: Genya Kolomeisky & Israel Klich]
ABSTRACT:

This talk deals with measurements of small forces at sub-micron separations. It tries to address an innocent enough question: Is Newtonian gravity valid at all distances? I will try to convey the deep sense of ignorance we still have in this topic, and describe the efforts undertaken to advance our knowledge. In particular, our experiments are sensitive to Yukawa-like corrections (i.e. interactions mediated by massive bosons) in the 0.1 to 1 micron range.

It will be shown that when trying to measure the gravitational interaction at short separations (on the order of 100 nm), other forces have to be taken into account. Among them, vacuum fluctuations are the more ubiquitous ones.

A brief description of how macroscopic bodies (classical objects) interact with vacuum fluctuations (a purely quantum effect) will be presented… towards developing approaches that are insensitive to them! These approaches use an  engineered sample which allows to establish better constraints in Yukawa-like interactions. This is accomplished by measuring the difference in forces in configurations where vacuum fluctuations are the same, but the corrections to Newtonian gravity (if any) are not.

Colloquium
Friday, October 31, 2014
3:30 PM
Physics Building, Room 204

 Available Colloquium Friday, October 24, 2014 3:30 PM Physics Building, Room 204  Add to your calendar

## "Fermion space charge in narrow-band gap semiconductors, Weyl semimetals and around highly charged nuclei"

Genya Kolomeisky , University of Virginia
[Host: Dinko Pocanic]
ABSTRACT:

The field of charged impurities in narrow-band gap semiconductors and Weyl semimetals can create electron-hole pairs when the total charge $Ze$ of the impurity exceeds a value $Z_{c}e.$ The particles of one charge escape to infinity, leaving a screening space charge. The result is that the observable dimensionless impurity charge $Q_{\infty}$ is less than $Z$ but greater than $Z_{c}$. There is a corresponding effect for nuclei with $Z >Z_{c} \approx 170$, however in the condensed matter setting we find $Z_{c} \simeq 10$. Thomas-Fermi theory indicates that $Q_{\infty} = 0$ for the Weyl semimetal, but we argue that this is a defect of the theory. For the case of a highly-charged recombination center in a narrow band-gap semiconductor (or of a supercharged nucleus), the observable charge takes on a nearly universal value. In Weyl semimetals the observable charge takes on the universal value $Q_{\infty} = Z_{c}$ set by the reciprocal of material's fine structure constant.

SLIDESHOW:
Colloquium
Friday, October 17, 2014
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "The Sacred Volcano, and other true stories from North Korea"

Richard Stone , American Association for the Advancement of Science
[Host: Seunghun Lee]
Colloquium
Friday, October 10, 2014
3:30 PM
Physics Building, Room 204

## "Non-WIMPy Dark Matter Searches at Fermilab"

William Wester , Fermilab
[Host: Craig Group]
ABSTRACT:

With the observation of the Higgs Boson in July 2012, high energy physics has claimed victory in accounting for all the known particles within the Standard Model of Particle Physics. However, great and profound questions remain unanswered regarding the nature of energy, matter, space and time. Among these questions is "What is the nature of Dark Matter" that accounts for approximately 80% of the matter in the universe. Gaining popularity is to invoke the possibility that "Non-WIMPy" new particles form the dark matter in contrast to usual Weakly Interacting Massive Particles hypothesis. Novel ideas and novel experiments, often at a very small scale, are exploring large areas of previously unexplored parameter space. Plus, they are a lot of fun too!

SLIDESHOW:
Colloquium
Friday, October 3, 2014
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "AS I REMEMBER. A Walk Through My Years at Hughes Aircraft"

Scott Walker , Hughes Aircraft and GM Hughes Electronics
[Host: Joe Poon]
ABSTRACT:

The basic theme of the talk is to emphasize the value of a physics degree when dealing with a wide spectrum of technical products and systems. Following the story line of his career as presented in his recent autobiography “As I Remember”, Scott will discuss the development of a number of military systems, US and international. In a light handed manner, he will summarize some community projects such as the Discovery Science Center in southern California, funding of a tax initiative for improved local transportation, and the formation by local businesses of the Robert Saunders scholarship for the school of engineering at UC Irvine. He will relate his physics background to the development of new semiconductor components and advanced automotive electronics, including the development of the EV-1, the first US commercial all electric vehicle by GM.

Bio: Dr. Walker received his Ph.D. in nuclear physics from the University of Virginia in 1961. Moving to California upon graduation, he joined Hughes Aircraft Company later to become GM Hughes Electronics. Over the next 37 years at Hughes he was given increasingly wide management responsibilities for the design and production of military systems, advanced industrial electronic components, international programs for air traffic control systems, both military and commercial, and advanced automotive electronics. Retiring in 1997 as Corporate Senior Vice President and member of the Office of the Chairman, Scott and his wife of fifty six years now reside in Indianapolis, Indiana.

SLIDESHOW:
Colloquium
Friday, September 26, 2014
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Hoo's going to help me? START to help you keep the evidence"

Ralph Allen , University of Virginia, Environmental Health & Safety
[Host: Rick Marshall]
ABSTRACT:

Accidents in academic research labs around the country have called attention to the lack of attention to safety when researchers assume that students understand the risks in their labs. Many of the hazardous materials have become increasingly regulated and granting agencies are now demanding evidence that environmental and safety regulations are followed. The first thing that regulators review are training records. The Office of Environmental Health and Safety has developed a program to help researchers document training and assist in improving laboratory safety.

SLIDESHOW:
Colloquium
Friday, September 19, 2014
3:30 PM
Physics Building, Room 203

Slideshow (PDF)

## "Quantum microscopy with NV centers in diamonds"

Alex Retzker , The Hebrew University of Jerusalem
[Host: Israel Klich]
ABSTRACT:

In recent years there has been a growing effort to develop a new type of microscopy, which is based on the NV (Nitrogen Vacancy) centers in diamonds. In this colloquium I will overview the latest results in this field and present a few quantum enhanced measurement schemes to image single protons using NV centers in diamond. These schemes will use ideas from quantum coherent control and quantum computing and will mainly target imaging with biological goals.

SLIDESHOW:
Colloquium
Friday, September 12, 2014
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, September 5, 2014 3:30 PM Physics Building, Room 204  Add to your calendar

## "The Life and Death of a Drop: Transitions and Singularities"

Sidney Nagel , University of Chicago
[Host: Seunghun Lee]
ABSTRACT:

The exhilarating spray from waves crashing onto the shore, the distressing sound of a faucet leaking in the night, and the indispensable role of bubbles dissolving gas into the oceans are but a few examples of the ubiquitous presence and profound importance of drop formation and splashing in our lives. They are also examples of a liquid changing its topology as it breaks into pieces. Although part of our common everyday experience, these changes are far from understood and reveal profound surprises upon careful investigation. For example, in droplet fission the fluid forms a neck that becomes vanishingly thin at the point of breakup so that there is a dynamic singularity in which physical properties such as pressure diverge. Singularities of this sort often organize the overall dynamical evolution of nonlinear systems. In this lecture, I will give the life history of a drop – from its birth to its eventual demise – illustrating the passage of its existence with the scientific surprises that determine its fate.

Colloquium
Friday, August 29, 2014
3:30 PM
Physics Building, Room 204

## "Unknowns of energy concentrating phenomena"

Seth Putterman , UCLA
[Host: Israel Klich]
ABSTRACT:
The path to equilibrium is not controlled by entropy production. Although entropy increases with every time step, dynamical motion can be dominated by nonlinear physical processes that spontaneously concentrate energy density. In sonoluminescence a bubble concentrates the energy of a traveling sound wave by 12 orders of magnitude to create picoseconds flashes of blackbody radiation that originate in a new state of matter. When surfaces are brought into and out of contact they exchange charge: a process called tribo-electrification. This phenomenon can be so strong that the power applied to peel sticky tape is efficiently transduced into a flux of high energy electrons, and x-ray photons that can expose an image in a few seconds. For a ferroelectric crystal, instabilities in the phonon spectrum lead to a spontaneous polarization that for Lithium Niobate reaches 15.million volts per cm. The temperature dependence of this field can be used to build a neutron generator based on the fusion of deuterium nuclei. These phenomena challenge a reductionist approach to the theoretical physics of emergent phenomena. The degree to which the energy density of a continuous system can be concentrated by off-equilibrium motion has not been determined by theory. For sonoluminescence, we do not know if the parameter space includes a region where an extra factor of 100 in energy density makes it possible to realize thermonuclear fusion. For triboelectrification, we do not have an ab-initio theory of charge transfer. And for ferroelectrics we do not have an ab-initio theory of the limits of spontaneous polarization which can be designed.
Colloquium
Friday, April 25, 2014
3:30 PM
Physics Building, Room 204

## "String Theory, Our Real World, and Higgs bosons"

Gordon Kane , University of Michigan
[Host: Dinko Pocanic]
ABSTRACT:
String theory is exciting because it can address most or all of the questions we hope to understand about the physical world, about the quarks and leptons that make up our world, and the forces that act on quarks and electrons to form our world, cosmology, and much more. Itâs nice that it provides a quantum theory of gravity too. Iâll explain why string theory is testable in basically the same ways as the rest of physics, why many people including string theorists are confused about that, and how string theory is already or soon being tested in several ways, including Higgs boson physics and LHC physics.
SLIDESHOW:
Colloquium
Friday, April 18, 2014
3:30 PM
Physics Building, Room 203

INPP Second Annual Lecture

Slideshow (PDF)

## "Unveiling the order of the high temperature superconductors"

Subir Sachdev , Harvard University
[Host: Seunghun Lee]
ABSTRACT:
A central mystery posed by the Cu-based high temperature superconductors has been the nature of their electronic state at low hole density. I will survey the remarkable progress made by recent experiments towards solving this mystery. The experiments show that there is a density-wave order with d symmetry. This is distinct from the d symmetry of the wavefunction of the Cooper pairs responsible for the superconductivity. I will review theories which anticipated these developments.
Colloquium
Friday, April 11, 2014
3:30 PM
Physics Building, Room 204

## "Whither Quantum Computing?"

Barry Sanders , University of Calgary
[Host: Niranjan Sridhar]
ABSTRACT:
A working quantum computer would be revolutionary because certain problems, such as simulating quantum materials or factorization, are easily solved on a quantum computer and probably forever hard on non-quantum computers no matter how small or how fast. Quantum computing technology is at an early stage so we do not yet know which medium is best. I discuss the principles of quantum computing, technological efforts for its realization (embellished with animated films), and applications for when a quantum computer eventually works.
SLIDESHOW:
Colloquium
Friday, April 4, 2014
3:30 PM
Physics Building, Room 204

Colloquium: Optical Society of America, UVA Student Chapter

Slideshow (PDF)

## "Quantum Networks in Quantum Optics"

H. Jeff Kimble , Caltech
ABSTRACT:

This talk will discuss the opportunities for the exploration of physical systems that have not heretofore existed in the natural world.

Colloquium
Thursday, March 27, 2014
7:00 PM
Chemistry 402, Room 402

Hoxton Lecture

## "Quantum computing with hypercubes of light"

Pei Wang , University of Virginia
[Host: Olivier Pfister]
ABSTRACT:
Quantum computing promises exponential speedup for particular computational tasks, such as factoring integers[1] and quantum simulation[2]. There are two main flavors of quantum computing: the circuit model and the measurement-based model---in particular, one-way quantum computing [3], which is implemented by applying measurements on an entangled resource known as a cluster state. Complicated computation tasks require the scalable generation of cluster states, which remains a formidable challenge. Pfisterlabs at UVa has been working on generating scalable cluster states and has successfully built some interesting cluster states [4,5].

In this colloquium, I will first explain continuous variable one-way quantum computing, cluster states, and then present our new proposal of a simple, "top-down" setup to generate large-size, D-hypercubic-lattice CV cluster states of more than 6000 entangled modes using D identical optical parametric oscillators (OPOs), each with a two-frequency pump [6]. These cluster states are sufficient for universal one-way quantum computation [3], and the high dimensional lattices are useful in quantum error correction based on Kitaev's surface code [7]. Our optical construction methods eschews the limitations of a three-dimensional world, enabling simulation of measurements on these high-valence cluster graphs and also inviting theoretical and experimental investigations of their topological properties [8].

References:
1. P.W.Shor, in Proceedings, 35th Annual Symposium on Foundations of Computer Science, edited by S.Goldwasser(IEEE press, Los Alamitos, CA, Santa Fe, NM,1994) pp. 124-134.
2. R.P.Feynman, Int.J.Theor.Phys.21,467 (1982)
3. R.Raussendorf and H.J.Briegel, "A one-way quantum computer", Phys.Rev.Lett. 86,5188(2001)
4. M.Pysher et al., "Parallel generation of quadripartite cluster entanglement in the optical frequency comb", Phys.Rev.Lett. 107, 030505(2011)
5. M.Chen, N.C.Menicucci,and O.Pfister,"Experimental realization of multipartite entanglement of 60 modes of the quantum optical frequency comb", arXiv:1311.2957[quant-ph](2013)
6. P.Wang, M.Chen, N.C.Menicucci,and O.Pfister,"Weaving quantum optical frequency combs into hypercubic cluster states", arXiv:1309.4105[quant-ph] (2013)
7. R.Raussendorf, J.Harrington, and K.Goyal,"A fault-tolerant one-way quantum computer", Ann. Phys.(N.Y.) 321, 2242â2270 (2006)
8. T. F. Demarie, T. Linjordet, N. C. Menicucci, and G. K. Brennen, Detecting Topological Entanglement Entropy in a Lattice of Quantum Harmonic Oscillators, arXiv:1305.0409 [quant-ph] (2013)

SLIDESHOW:
Colloquium
Friday, February 21, 2014
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "String Theory, Our Real World, and Higgs bosons"

Gordon Kane , University of Michigan
[Host: Dinko Pocanic]
ABSTRACT:
String theory is exciting because it can address most or all of the questions we hope to understand about the physical world, about the quarks and leptons that make up our world, and the forces that act on quarks and electrons to form our world, cosmology, and much more. Itâs nice that it provides a quantum theory of gravity too. Iâll explain why string theory is testable in basically the same ways as the rest of physics, why many people including string theorists are confused about that, and how string theory is already or soon being tested in several ways, including Higgs boson physics and LHC physics.
Colloquium
Friday, February 14, 2014
3:30 PM
Physics Building, Room 203

INPP Second Annual Lecture

## "Universality in the Magnetic Response of Metamagnetic Materials"

Pradeep Kumar , University of Florida
[Host: Bellave Shivaram]
Colloquium
Friday, January 31, 2014
3:30 PM
Physics Building, Room 204

## "Non-equilibrium statistical physics, population genetics and evolution"

Marija Vucelja , Rockefeller University
[Host: Joe Poon]
ABSTRACT:
I will present a glimpse into the fascinating world of biological complexity from the perspective of theoretical physics. Currently the fields of evolution and population genetics are undergoing a renaissance, with the abundance of accessible sequencing data. In many cases the existing theories are unable to explain the experimental findings. The least understood aspects of evolution are intrinsically quantitative and statistical and we are missing a suitable theoretical description. It is not clear what sets the time scales of evolution, whether for antibiotic resistance, emergence of new animal species, or the diversification of life. I will try to convey that physicists are invaluable in framing such pertinent questions. The emerging picture of genetic evolution is that of a strongly interacting stochastic system with large numbers of components far from equilibrium. In this colloquium I plan to focus on the dynamics of evolution. I will discuss evolutionary dynamics on several levels. First on the microscopic level - an evolving population over its history explores a small part of the whole genomics sequence space. Next I will coarse-grain and review evolutionary dynamics on the phenotype level. I will also discuss the importance of spatial structures and temporal fluctuations. Along the way I will point out similarities with physical phenomena in condensed matter physics, polymer physics, spin-glasses and turbulence.
SLIDESHOW:
Colloquium
Friday, December 6, 2013
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Neutrinos: Masters of Surprise"

Bob McKeown , Jefferson Lab
[Host: Nilanga Liyanage & Gordon Cates]
ABSTRACT:
In the recent past the experimental study of neutrinos has yielded a series of surprising results. The very light masses and strong flavor mixing have challenged theorists and also motivated experimentalists to perform ever more sensitive experiments. In this colloquium I will discuss these developments, including the observation of the unexpectedly large mixing angle θ13 by the Daya Bay reactor neutrino experiment. Prospects for future studies, and opportunities for additional surprises, will also be discussed.
SLIDESHOW:
Colloquium
Friday, November 22, 2013
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Recent Discoveries of Cosmic Ray Anomalies"

Eun-Suk Seo , University of Maryland
[Host: Craig Group]
SLIDESHOW:
Colloquium
Friday, November 15, 2013
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Majorana Materializes"

Jason Alicea , Caltech
[Host: Paul Fendley]
ABSTRACT:
The 1937 theoretical discovery of Majorana fermions (particles that are their own anti-particles) has since impacted diverse problems ranging from neutrino physics and dark matter searches to the quantum Hall effect and superconductivity. This talk will survey recent revolutionary advances in the condensed matter pursuit of these elusive objects. In particular, I will discuss new ways of "engineering" Majorana platforms using exceedingly simple building blocks, along with pioneering experiments that have made impressive progress towards realizing Majorana fermions. These developments mark the first steps of a fascinating research program that could eventually overcome one of the grand challenges in the fieldâthe synthesis of a scalable quantum computer.
SLIDESHOW:
Colloquium
Friday, October 25, 2013
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Particle and Nuclear physics with cold neutrons"

Nadia Fomin , University of Tennessee, Knoxville
[Host: Dinko Pocanic]
SLIDESHOW:
Colloquium
Friday, October 4, 2013
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Experiences with a "Jackson by Inquiry" electromagnetism course and the connection with neural networks, recent cognitive neuroscience, and modern theories of teaching/learning"

Bruce Patton , The Ohio State University
[Host: Joe Poon]
ABSTRACT:
The electromagnetism course is often a singular experience in the education of a physics student, graduate and undergraduate. We described recent experiments to deliver the highly technical material in the electromagnetism course in an active learning studio lab format that current physics education research suggests is more optimal. Exploration of the results leads to connections with neuronal network models of the brain, modern neurophysiology and cognitive science, a simple phenomenological model of the teaching/learning process, and optimal design of the learning environment.
Colloquium
Friday, September 27, 2013
3:30 PM
Physics Building, Room 204

## "The Interplay Between the Top Quark and the Higgs Boson: How a discovery from a generation ago can help us understand the latest breakthrough in particle physics"

Chris Neu , University of Virginia
[Host: Joe Poon]
ABSTRACT:
The recent discovery at the LHC of a new fundamental particle has generated a significant amount of excitement around the globe -- an excitement unmatched in particle physics since the discovery of the top quark in 1995. Given its observed decay channels, its mass and a handful of its properties, indications are that this new particle could be the long-sought Higgs boson, the particle which is purported to be the linchpin in understanding the imposition of mass to the fundamental particles. However much remains to be known -- it could be the Higgs boson predicted by the standard model or it could be something more exotic. Complete characterization of this new particle must be done in order to understand its true nature; its interactions with the top quark will play a vital role in this endeavor. Herein I describe the importance the top quark will play in studies of this new particle, and describe in detail one particularly important channel in the characterization effort: the search for production of the Higgs boson in association with top-quark pairs at CMS.
SLIDESHOW:
Colloquium
Friday, September 20, 2013
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

 Graduate Townhall Meeting Colloquium Friday, September 6, 2013 3:30 PM Physics Building, Room 204  Add to your calendar

## "When a theorist met an experimentalist or vice versa"

Israel Klich & Seunghun Lee , University of Virginia
[Host: Joe Poon]
SLIDESHOW:
Colloquium
Friday, August 30, 2013
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Bloch, Landau, and Dirac: Hofstadter's Butterfly in Graphene"

Philip Kim , Columbia University
[Host: Seunghun Lee]
ABSTRACT:
Electrons moving in a periodic electric potential form Bloch energy bands where the mass of electrons are effectively changed. In a strong magnetic field, the cyclotron orbits of free electrons are quantized and Landau levels forms with a massive degeneracy within. In 1976, Hofstadter showed that for 2-dimensional electronic system, the intriguing interplay between these two quantization effects can lead into a self-similar fractal set of energy spectrum known as "Hofstadter's Butterfly." Experimental efforts to demonstrate this fascinating electron energy spectrum have continued ever since. Recent advent of graphene, where its Bloch electrons can be described by Dirac fermions, provides a new opportunity to investigate this half century old problem experimentally. In this presentation, I will discuss the experimental realization Hofstadter's Butterfly via substrate engineered graphene under extremely high magnetic fields controlling two competing length scales governing Dirac-Bloch states and Landau orbits, respectively.
SLIDESHOW:
Colloquium
Friday, April 26, 2013
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "The World According to Higgs"

Chris Quigg , Fermi National Accelerator Laboratory
ABSTRACT:

New developments in particle physics offer a new and radically simple conception of the universe. Fundamental particles called quarks and leptons make up everyday matter, and two new laws of nature rule their interactions. Until July 4, 2012, our neat story was missing one piece, a particle called the Higgs boson. Without it, there would be no atoms, no chemistry, no liquids or solids, and no basis for life. Why did thousands of physicists devote decades to the hunt, and how does the “discovery of the century” change the way we see the world?

Colloquium
Thursday, April 18, 2013
7:00 PM
Chemistry Building, Room Chemistry 402

Hoxton Lecture

## "Nonlinear optics at the nanoscale Physics"

Eric Mazur , Harvard University
[Host: Kevin Lehmann & Brad Cox]
Colloquium
Friday, April 12, 2013
4:00 PM
Physics Building, Room 203

Joint Chemistry & Physics Colloquium

## "Current Results in Neutrino Physics"

Christopher White , Illinois Institute of Technology
[Host: Craig Dukes]
ABSTRACT:
Despite decades of research, neutrinos are still one of the least understood fundamental particles. Despite a world-wide experimental effort over the past 20 years that has started to reveal the neutrino's secrets, there is much more to be learned. One of the hopes is that a detailed study of neutrino properties will help us understand the observed asymmetry between matter and antimatter in the universe. It is also becoming clear that neutrinos play a key role in a variety of astrophysical phenomena, such as supernova explosions. I will review what is currently known about neutrinos as well as near and longer term experimental efforts.
Colloquium
Friday, April 5, 2013
4:00 PM
Physics Building, Room 204

## "Medical applications of nuclear physics"

Thia Keppel , Jefferson Lab
[Host: Nilanga Liyanage]
Colloquium
Friday, March 29, 2013
4:00 PM
Physics Building, Room 204

## "Emergent phenomena and universality in quantum systems far from thermal equilibrium"

Ehud Altman , Weizmann Institute
[Host: Israel Klich]
ABSTRACT:
Recent experiments with ultra-cold atomic gases and trapped ions as well as solid-state devices such as superconducting circuits designed to manipulate q-bits, are posing a new challenge for theory. As in traditional atomic physics these systems are often prepared far from equilibrium, or continuously driven by electromagnetic fields. At the same time they retain a many-body character and intricate quantum correlations, which define a new class of quantum matter. I will first review recent experimental advances in this field and then address a theoretical question: Can the complexity of quantum dynamics in these systems give rise to robust universal phenomena in spite of the non-equilibrium conditions?
SLIDESHOW:
Colloquium
Friday, March 1, 2013
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "The Physics IQ Test"

Richard Berg , University of Maryland
[Host: Craig Group]
ABSTRACT:
The assembled throngs vote on the outcome of counterintuitive "brainteaser" type physics questions, which are then answered by performing simple physics demonstration experiments. One interesting result is that the average score is about the same for groups ranging from high school students to physics professors.
SLIDESHOW:
Colloquium
Friday, February 22, 2013
4:00 PM
Physics Building, Room 203

Joint Colloquium: Physics Department & Society of Physics Students

Slideshow (PDF)

## "Superconducting Quarks: Condensed Matter in the Heavens"

Mark Alford , Washington University in St. Louis
[Host: Diana Vaman]
ABSTRACT:
In this talk I will describe the densest predicted state of matter—color-superconducting quark matter. A color superconductor is very different from an "ordinary" electrical superconductor: it occurs at ultra-high density and has a much richer phase structure because quarks come in many varieties. This form of matter may well exist in the core of neutron stars, and the search for signatures of its presence is currently proceeding. I will give an accessible review of the features of color-superconducting quark matter, and discuss some ideas for finding it in nature.
SLIDESHOW:
Colloquium
Friday, February 1, 2013
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Exploring topological states with cold atoms and photons"

Eugene Demler , Harvard University
[Host: Israel Klich]
ABSTRACT:
I will review recent theoretical ideas and experimental realizations of topological states using ultracold atoms in optical lattices and quantum walk protocols with photons. Such systems enabled several types of measurements, which had not been possible in solid state systems, including direct measurements of the Berry/Zak phases of Bloch bands and observation of edge states on domain walls in the one dimensional SSH model. I will also discuss new types of topological states in periodically modulated Floquet-Bloch bands which have been realized in photon quantum walks.
Colloquium
Friday, January 18, 2013
4:00 PM
Physics Building, Room 204

## "Clusters, Correlations, and Quarks: A High-Energy Perspective on Nuclei"

John Arrington , Argonne National Laboratory
[Host: Donal Day]
ABSTRACT:
While nuclei form the core of matter, an understanding of their structure in terms of their fundamental constituents, quarks and gluons, is still well out of reach due to the complex nature of quark interactions in Quantum chromodynamics (QCD). Therefore, "effective" models of nuclei are needed as input for different measurements, from the simple collection of quasifree quarks used in high energy scattering measurements to complex shell structure studied in low energy nuclear physics. These models are useful because of the large separation between the natural energy and distance scales associated with QCD, nuclear binding, and atomic physics. However, there are regions where interactions at vastly different scales have non-trivial interactions which can be seen in high-precision measurements or for specific, well-chosen observables. I will provide some examples of this mixing of energy scales and then focus on the overlap between the scales relevant for nuclear structure and those probed in medium- and high-energy studies of nucleon structure. High-density configurations and large virtual excitations in nuclei provide increased interplay between nuclear scales and QCD, providing opportunities for higher energy measurements to probe details of nuclear structure, and yielding phenomena where low energy nuclear structure may impact the quark description of matter.
SLIDESHOW:
Colloquium
Friday, December 7, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "The Supernova Early Warning System (SNEWS)"

Alec Habig , University of Minnesota Duluth
[Host: Craig Dukes]
ABSTRACT:
SNEWS is a cooperative effort between the world's neutrino detection experiments to spread the news that a star in our galaxy has just experienced a core-collapse event and is about to become a Type II Supernova. This project exploits the ~hours time difference between neutrinos promptly escaping the nascent supernova and photons which originate when the shock wave breaks through the stellar photosphere, to give the world a chance to get ready to observe such an exciting event at the earliest possible time. A coincidence trigger between experiments is used to eliminate potential local false alarms, allowing a rapid, automated alert. A new experiment which will participate in SNEWS is the Helium and Lead Observatory. HALO is a new, dedicated supernova neutrino experiment being built in SNOLAB from a combination of lead and the SNO experiment's old He3 neutron counters. It is designed to be a low-maintenance, high-livetime, and long-lived experiment to complement existing, multi-purpose neutrino detectors.
SLIDESHOW:
Colloquium
Friday, November 30, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Topological Band Theory and Twisted Multilayer Graphene"

Gene Mele , University of Pennsylvania
[Host: Genya Kolomeisky]
ABSTRACT:
Topological insulators are a recently discovered quantum electronic phase of matter. This talk will give a brief overview of the known electronic phases of matter, focusing on the unique properties of topological insulators and their discovery from a careful consideration of the low energy electronic physics of single-layer graphene. Closely related topological ideas are then used to analyze the mysterious electronic behavior of a family of multilayer graphenes known as âtwistedâ graphenes in which a rotation of neighboring layers leads to unexpectedly rich low energy physics.
SLIDESHOW:
Colloquium
Friday, November 16, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Bright Coherent Ultrafast X-Ray Beams on a Tabletop and Applications in Nano and Materials Science"

Margaret Murnane , University of Colorado at Boulder
[Host: Reihaneh Shahrokhshahi]
ABSTRACT:
Ever since the invention of the laser 50 years ago, scientists have been striving to extend coherent laser-like beams into the x-ray region of the spectrum. Very recently, the prospects for tabletop x-ray beams at wavelengths <10Ã have brightened considerably. This advance is the direct result of a new ability to manipulate electrons on their natural, attosecond (10^-18s), time-scales using femtosecond lasers. In recent work we uncovered a new regime of nonlinear optics, where bright laser-like X-ray supercontinua with photon energies >1.6keV (wavelengths < 8Ã) can be produced from a tabletop femtosecond laser [1]. This represents the most extreme >5001 order nonlinear optical process known. X-rays are powerful probes of the nanoworld. They penetrate thick samples and can image small objects. This talk will also highlight how ultrafast x-rays can capture the coupled motions of charges, spins, phonons and photons that underlie function on the fastest timescales. [2,3]
1. Popmintchev et al, Science 336, 1287 (2012).
2. Mathias, et al, PNAS 109, 4792 (2012).
3. Rudolf et al., Nature Commun 3, 1037 (2012).
SLIDESHOW:
Colloquium
Friday, November 9, 2012
4:00 PM
Physics Building, Room 204

Colloquium: Optical Society of America, UVA Student Chapter

Slideshow (PDF)

## "Holograms of strings"

Diana Vaman , University of Virginia
[Host: Joe Poon]
SLIDESHOW:
Colloquium
Friday, October 12, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Precision studies of the nucleon"

Nilanga Liyanage , University of Virginia
[Host: Joe Poon]
Colloquium
Friday, October 5, 2012
4:00 PM
Physics Building, Room 204

## "Fundamental physics with free neutrons"

Stefan Baessler , University of Virginia
[Host: Joe Poon]
SLIDESHOW:
Colloquium
Friday, September 28, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Quantum fluctuations: From the Casimir Effect to Quantum Entanglement"

Israel Klich , University of Virginia
[Host: Joe Poon]
ABSTRACT:
In the world of quantum mechanics, nothing is certain, including the meaning of "nothing". Indeed, the Casimir effect, an attraction between two mirrors separated by vacuum, sometimes called âA force from nothingâ, is an example of the intricate consequences of taking quantum mechanics seriously. The Casimir effect has been in the spotlight in the last decade, as its importance beyond fundamental physics and its experimental demonstration have been realized. The effect is gaining relevance in areas as diverse as cosmology, quantum field theory, condensed matter physics, biology and nanotechnology. In this talk, I will explore the role of quantum fluctuations, and radiation matter coupling in creating this force, as well as present new results on another aspect of quantum fluctuations of great importance: that of entanglement. In particular, I will explore the entanglement between radiation and matter in a framework inspired by the Casimir effect.
Colloquium
Friday, September 21, 2012
4:00 PM
Physics Building, Room 204

## "Higgs Boson Searches at the CDF Experiment: Highlights of UVa Contributions to a Successful Search with the Full Data Set"

Craig Group , University of Virginia
[Host: Joe Poon]
ABSTRACT:
I present the results from the CDF experiment on the direct searches for a Standard Model Higgs boson produced in p-pbar collisions at a center of mass energy of 1.96 TeV, using the data corresponding to integrated luminosity of up to 10fb－1. The searches are performed in the Higgs boson mass range from 100 to 200 GeV/c2. The dominant decay channels, H → bb and H → W W , are combined with all the secondary channels and significant analysis improvements have been recentlyimplemented to maximize the search sensitivity. UVa contributions to these analyses, their recent improvements, and to the leadership of the effort are highlighted. The results from the CDF experiment are combined with the D0 experiment, both using their full data sets, and a significant excess of data events compared to background prediction is reported. The highest local significance is 3.0 standard deviations while global significance for such an excess anywhere in the full mass range investigated is approximately 2.5 standard deviations. Both experiments at the Large Hadron Collider have recently reported excesses of greater than 5standard deviations in their searches for the Higgs boson. The complementarity and relevance of the Tevatron results are discussed in the context of this recent discovery from the LHC.
SLIDESHOW:
Colloquium
Friday, September 14, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Devoting your life to scientific research does not mean that you should actually risk your life and granting as well as regulatory agencies will make sure that you don't"

Ralph Allen , University of Virginia
[Host: Rick Marshall]
ABSTRACT:
Accidents in academic research labs around the country have called attention to the lack of attention to safety when researchers assume that students understand the risks in their labs. Many of the hazardous materials have become increasingly regulated and granting agencies are now demanding evidence that environmental and safety regulations are followed. The first thing that regulators review are training records. The Office of Environmental Health and Safety has developed a program to help researchers document training and assist in improving laboratory safety.
Colloquium
Friday, September 7, 2012
4:00 PM
Physics Building, Room 204

## "Graphene: how electrons move and interact in the ultimate flatland"

Enrico Rossi , College of William & Mary
[Host: Genya Kolomeisky]
ABSTRACT:
Graphene is a one atom-thick layer of carbon atoms arranged in a two-dimensional honeycomb lattice that was first realized in a laboratory in 2004. In graphene the electrons are strictly con fined to live in two dimensions and behave as massless Dirac fermions described by two-dimensional Quantum Electro Dynamics (QED), albeit with a much lower (1/300 th) speed of light and bigger (≈ 1), and tunable, fine structure constant. Due to its unique electronic structure graphene exhibits anomalous electronic properties. In this talk I will discuss the unusual transport properties of graphene and provide a theoretical explanation of the "puzzles" posed by graphene transport measurements since its discovery. I will then discuss the eff ect of electron-electron interactions. Most of the experiments suggest that in single layer graphene the interactions have only a quantitative eff ect. However, recently very high quality graphene heterostructures have been realized and the experimental measurements conducted on them suggest that in these structures the interactions can drive the electrons into novel spontaneously broken symmetry ground states. I will present our theoretical study of "hybrid" heterostructures formed by one sheet of single layer graphene and one sheet of bilayer graphene and show that in these structures the spontaneously broken symmetry ground state is 2-fold degenerate with one of the degenerate states analogous to a superfluid chiral state. The chiral nature of one of the degenerate ground states opens the possibility to observe in graphene heterostructures topologically protected midgap states analogous to Majorana modes.
Colloquium
Friday, August 31, 2012
4:00 PM
Physics Building, Room 204

## "101 Years of Superconductivity - My Contributions Therein"

Bellave Shivaram , University of Virginia
ABSTRACT:
Starting from a brief history of its initial discovery I will trace the development/study of various classes of superconducting materials. I will cover the phenomenology in these different classes with references to microscopic theory where appropriate, and also present a concurrent description of my own experimental contributions.
Colloquium
Friday, April 27, 2012
4:00 PM
Physics Building, Room 204

## "The National Ignition Facility: Pathway to Energy Security and Physics of the Cosmos"

Edward Moses , National Ignition Facility
ABSTRACT:

The National Ignition Facility (NIF), at Lawrence Livermore National Laboratory in Livermore, California, is the world’s most energetic laser system. NIF is capable of producing over 1.8 MJ and 500 TW of ultraviolet light, 100 times more than any other operating laser. Completed in March 2009, it is maturing rapidly and transitioning into the world’s premier high-energy-density science experimental facility, while supporting its strategic security, fundamental science, and energy security missions.

By concentrating intense laser energy into target only millimeters in length, NIF can, for the first time, produce conditions emulating those found in planetary interiors and stellar environments and creating fusion energy to power our future. The extreme conditions of energy density, pressure, and temperature will enable scientists to pursue fundamental science experiments designed to address a range of scientific questions, from observing new states of matter to exploring the origin of ultrahigh-energy cosmic rays. Early experiments have been successfully completed in support of materials equations of state, materials strength, and radiation transport in extreme temperature and pressure conditions.

The National Ignition Campaign, an international effort pursued on the NIF, aims to demonstrate fusion burn and generate more energy output than the laser energy delivered to the target. Achieving this ignition goal will validate the viability of inertial fusion energy (IFE) as a clean source of energy. A laser-based IFE power plant will require advances in high-repetition-rate lasers, large-scale target fabrication, target injection and tracking, and other supporting technologies. These capabilities could lead to an operational prototype IFE power plant in 10 to 15 years. LLNL, in partnership with academia, national laboratories, and industry, is developing a Laser Inertial Fusion Energy (LIFE) baseline design concept and examining technology choices for developing a LIFE prototype power plant.

This talk will describe the unprecedented experimental capabilities of the NIF, its role in strategic security and fundamental science, and the pathway to achieving fusion ignition to create a clean and secure energy future.

Colloquium
Thursday, April 12, 2012
7:00 PM
Chemistry Building, Room 402

Special Colloquium: Hoxton Lecture

## "Fundamental measurements of the proton's sub-structure using high-energy polarized proton-proton collisions "

Bernd Surrow , Temple University
[Host: Nilanga Liyanage]
ABSTRACT:
Understanding the structure of matter in terms of its underlying constituents has a long tradition in science. A key question is how we can understand the properties of the proton, such as its mass, charge, and spin (intrinsic angular momentum) in terms of its underlying constituents: nearly massless quarks (building blocks) and massless gluons (force carriers). The strong force that confines quarks inside the proton leads to the creation of abundant gluons and quark-antiquark pairs (QCD sea). These âsilent partnersâ make the dominant contribution to the mass of the proton. Various polarized deep-inelastic scattering measurements have shown that the spins of all quarks and antiquarks combined account for only 25% of the proton spin. New experimental techniques are required to deepen our understanding on the role of gluons and the QCD sea to the proton spin. High energy polarized proton-proton (p + p) collisions at RHIC at Brookhaven National Laboratory provide a new and unique way to probe the proton spin structure using very well established processes in high-energy physics, both experimentally and theoretically. A major new tool has been established for the first time using parity-violating W boson production in polarized p + p collisions at sÂ =Â 500Â GeV demonstrating directly the different polarization patterns of different quark flavors, paving the path to study the polarization of the QCD sea. Various results in polarized p + p collisions at sÂ =Â 200Â GeV constrain the degree to which gluons are polarized suggesting that the contribution of the gluons to the spin of the proton is rather small, in striking contrast to their role in making up the mass of the proton.
SLIDESHOW:
Colloquium
Friday, April 6, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "A Scientific Analysis of 21st Century Environmental and Economic Challenges"

Sir David King , Smith School at Oxford
[Host: John T. Yates, Jr., Ian Harrison, & Brad Cox]
ABSTRACT:
Unprecedented improvements in human wellbeing over the nineteenth and twentieth centuries have been driven largely by developments flowing from advances in engineering, medicine, agriculture and technology, and by political and economic developments coupled to consumerism. But a necessary consequence of these successes has been an equally unprecedented growth in the global population. The twenty first century will be dominated by the challenges posed by a mid-century population of around 9 billion people, all seeking a high standard of living. Ecosystem services, an essential element of our continued wellbeing as a species, are already under threat as our need for food production, fresh water, energy sources, minerals etc. grows exponentially to meet unfettered demand. Climate change, driven by fossil fuel usage and by deforestation, provides the biggest challenge of all, since it requires a collective response of the global population, to mitigate the effect and to manage the growing impacts upon our societies.

Well designed technological solutions are desirable and can be compatible with the continued growth of human wellbeing. The socio-political challenges in directing such a collective response are beyond anything previously managed. This may well lead to a mid-century slide into conflict caused by environmental and resource-driven challenges on a scale not previously experienced. The thesis presented here is that meeting these challenges will require a global cultural and technological transformation on much the same scale as the European Renaissance or the Industrial Revolution itself, and a clear understanding by all societies of the need to adapt and strengthen global governance procedures. Decision making at all levels will require significantly enhanced knowledge and understanding.

Colloquium
Friday, March 23, 2012
4:00 PM
Physics Building, Room 203

## "Tales from the Darkside of Particle Physics"

Bill Marciano , Brookhaven National Laboratory
[Host: INPP]
ABSTRACT:
The "Minimal" Standard Model of particle physics is almost complete. Interesting hints of a standard Higgs Boson are starting to appear at CERN and one can ask, Is it all that remains to be discovered? Dark matter observations suggest that an invisible universe of massive particles may exist all around us, but coupled to normal matter primarily by gravity. Can we detect dark particles and study their properties at accelerators? In this talk, I will discuss the implications of a Higgs Boson discovery and speculate on its possible connection to "dark" matter physics. In particular, properties of the "dark" photon, a hypothetical "dark" force carrier, along with ongoing and proposed experimental efforts to discover, it will be described.
SLIDESHOW:
Colloquium
Thursday, March 15, 2012
3:30 PM
Physics Building, Room 203

Special Colloquium: Institute of Nuclear and Particle Physics Annual Lecture

Slideshow (PDF)

## "The Next Generation of Nuclear Reactor Designs"

Sama Bilbao Y Leon , Virginia Commonwealth University
[Host: Simonetta Liuti]
ABSTRACT:
There are today over 440 commercial nuclear power reactors operating in 30 countries. They provide about 14% of the world's electricity in the form of economic, environmentally sound and reliable base-load power. In addition, 63 new nuclear reactors are currently under construction in 14 countries. But much has changed in the design of nuclear reactors since the first commercial nuclear power stations started operating in the 1950s. Modern nuclear reactors, those that will be built in the short term, achieve improvements over existing designs through small to moderate modifications, with a strong emphasis on maintaining design provenness and building upon the lessons learnt from 40 years of successful operation, to minimize technological and investment risks. At the same time, nuclear designers are already working on a new generation of nuclear reactor concepts incorporating radical conceptual changes in design approaches or system configuration in comparison with existing practice. Substantial research and development efforts, feasibility tests, as well as a prototype or demonstration plant are probably required prior to the commercial deployment of these innovative designs. This talk will provide an overview of the most recent developments in nuclear reactor design, including those using alternative fuel cycles, such as Thorium.
SLIDESHOW:
Colloquium
Friday, March 2, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Imaging the microscopic structure of shear thinning and thickening colloidal suspensions"

Xiang Cheng , Cornell University
[Host: Seunghun Lee]
ABSTRACT:
While a simple Newtonian fluid such as water flows with a constant viscosity, many structured fluids ranging from polymer melts to surfactant solutions exhibit fascinating non-Newtonian flow behaviors including shear thinning and shear thickening. One typical example is a colloidal suspension, where its viscosity can vary by orders of magnitude depending on how quickly it is sheared. Although these non-Newtonian behaviors are believed to arise from the arrangement of suspended particles and their mutual interactions, microscopic particle dynamics in such suspensions are difficult to measure directly. Here, by combining fast confocal microscopy with simultaneous force measurements, we systematically investigate a suspension's structure as it transitions through regimes of different flow signatures. Our measurements of the microscopic single-particle dynamics unambiguously show that shear thinning results from the decreased relative contribution of entropic forces and that shear thickening arises from particle clustering induced by inter-particle hydrodynamic lubrication forces. Furthermore, we explore out-of-equilibrium structures of sheared colloidal suspensions and report a novel string phase, where particles link into log-rolling strings normal to the plane of shear. Our techniques illustrate an approach that complements current methods for determining the microscopic origins of non-Newtonian flow behavior in complex fluids.
Colloquium
Thursday, February 23, 2012
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Spin Ice and Quantum Spin Liquid in Geometrically Frustrated Magnets"

Haidong Zhou , National High Magnetic Field Lab
[Host: Seunghun Lee]
ABSTRACT:
In geometrically frustrated magnets (GFMs), the incompatibility between the interactions of the magnetic degrees of freedom in a lattice and the underling crystal geometry leads to the frustration. The massive level of degeneracy introduced by this frustration can persist to low temperatures to enhance the spin fluctuations and suppress the magnetic ordering, therefore resulting exotic spin ground states with abnormal thermo-dynamics. In this talk, two GFMs will be introduced: (i) Spin ice with pyrochlore structure, in which the ground state is a short range ordering of the âtwo spin in two spin outâ configurations on tetrahedrons following the âice ruleâ; (ii) Quantum spin liquid (QSL), in which the strong quantum fluctuations of the spins with small number (S = 1/2 and 1) destroy the magnetic ordering and lead to a spin-liquid like ground state. Following the introduction, we present our recently studies on new pyrochlore materials Pr2Sn2O7 and Dy2Ge2O7, and new QSL materials Ba3CuSb2O9 and Ba3NiSb2O9 with a triangular lattice of S = 1/2 and S = 1, respectively.
SLIDESHOW:
Colloquium
Monday, February 20, 2012
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Oxide Nanoelectronics on Demand"

Cheng Cen , IBM
[Host: Seunghun Lee]
ABSTRACT:
Complex oxides and their heterostructures have exhibited a great collection of novel functionalities and are considered one of the most promising candidate for next generation technological materials. At the interface formed between LaAlO3 and SrTiO3, by scanning a biased conducting atomic force microscope (AFM) tip along a programmed trajectory at room temperature, we can reversibly control in nanoscale the metal-insulator transition. With this technique, a variety of rewritable nanoscale devices and structures have been studied. These nanostructures, which are mainly assembled from basic elements including conductive wires and dots with characteristic dimensions just a few nanometers, show great performance as field effect transistors, nanodiodes and photodetectors. At low temperatures, a variety of electronic, spintronic and superconducting properties are observed, with enormous potential for exploitation in quantum devices.
Colloquium
Thursday, February 16, 2012
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Pseudo-spin Resolved Transport Spectroscopy of the Kondo Effect"

Sami Amasha , Stanford University
[Host: Seunghun Lee]
ABSTRACT:
In strongly-correlated materials, such as high-temperature superconductors and heavy fermion compounds, electrons form many-body states with properties different from those of non-interacting electrons. A simpler and better understood example of electron correlations is the Kondo effect, which describes how spins of conduction electrons screen the spin of a localized electron that has degenerate spin states (spin-up and spin-down in the case of a localized spin-1/2 electron). This screening generates spin correlations. Electrical transport measurements of a single quantum dot can probe Kondo physics; however, to directly access the spin correlations one needs spin-resolved measurements. We address this challenge by using the orbital states of a double quantum dot as pseudo-spin states: an electron on the left/right dot is associated with pseudo-spin up/down. When the energies of these pseudo-spin states are degenerate, Kondo screening occurs. We establish a correspondence between spin Kondo in a single dot and pseudo-spin Kondo in double dots. We use this to show that our pseudo-spin resolved spectroscopy measurements of the Kondo state in a double dot correspond to predictions for spin-resolved spectroscopy of spin Kondo. Finally, we explore the interplay between orbital and spin degeneracy in this double dot system.
Colloquium
Monday, February 13, 2012
3:30 PM
Physics Building, Room 204

Special Colloquium

Robert W. Michaels , Thomas Jefferson National Accelerator Facility
[Host: Xiaochao Zheng]
ABSTRACT:
The Lead Radius Experiment PREX ran in the Spring of 2010 in Hall A at the Thomas Jefferson National Accelerator Facility (JLab). The experiment measures the parity-violating asymmetry in the elastic scattering of longitudinally polarized electrons from a 208Pb nucleus at an energy of 1.06 GeV and a scattering angle of 5. The Z boson that mediates the weak neutral interaction couples mainly to neutrons and provides a clean, model-independent measurement of the RMS radius Rn of the neutron distribution in the nucleus. This measurement is a fundamental test of nuclear structure theory, and our result establishes the existence of the neutron skin, i.e. that Rn > Rp. A precise measurement of Rn pins down the density-dependence of the symmetry energy of neutronrich nuclear matter, which has impacts on neutron star structure, heavy ion collisions, and atomic parity violation experiments. The experiment involves all aspects of the JLab accelerator, from the polarized source to the detector, and capitalizes on JLabâs unique strengths for carrying out high-precision parity experiments. In addition to the 2010 data, several technical challenges will be described, as well as prospects for future measurements at JLab from 208Pb and other nuclei such as 48Ca.
SLIDESHOW:
Colloquium
Friday, February 10, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Tailoring Dirac Fermions in Molecular Graphene"

Kenjiro Gomes , Stanford University
[Host: Seunghun Lee]
ABSTRACT:
The dynamics of electrons in solids is tied to the band structure created by a periodic atomic potential. The design of artificial lattices, assembled through atomic manipulation, opens the door to engineer electronic band structure and to create novel quantum states. We present scanning tunneling spectroscopic measurements of a nanoassembled honeycomb lattice displaying a Dirac fermion band structure. The artificial lattice is created by atomic manipulation of single CO molecules with the scanning tunneling microscope on the surface of Cu(111). The periodic potential generated by the assembled CO molecules reshapes the band structure of the two-dimensional electron gas, present as a surface state of Cu(111), into a "molecular graphene" system. We characterize the band structure through Fourier transform analysis of impurity scattering maps. We tailor this new tunable class of graphene to reveal signature topological properties: an emergent mass and energy gap created by breaking the pseudospin symmetry with a Kekule bond distortion; gauge fields generated by applying atomically engineered strains; and the condensation of electrons into quantum Hall-like states and topologically confined phases.
Colloquium
Thursday, February 9, 2012
3:30 PM
Physics Building, Room 204

Special Colloquium

## "N-polaron systems and mathematics"

Lawrence Thomas , University of Virginia
[Host: Dinko Pocanic]
ABSTRACT:
The polaron is a mathematical model for a âdressedâ particle consisting of an electron together with its entourage of local excitations of a quantized phonon field. We will give a brief historical review of the polaron, including the analysis of its ground state by a Brownian motion functional integral and by a related variational expression.
For the case of two or more electrons, the interaction of the electrons with the phonon field gives rise to an effective attraction between electrons that causes the particles to bind together. For N electrons, N → ∞, the systems are unstable in the sense that the binding energy grows faster than linearly in N. We will discuss recent work with Frank, Lieb, and Seiringer which shows that sufficiently strong Coulomb repulsion between electrons can compensate for this binding and provide stability for polaron systems for large N.
SLIDESHOW:
Colloquium
Friday, January 27, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Characterizing phase diagram of High Temperature Superconductors via Angle Resolved Photoemission Spectroscopy"

Utpal Chatterjee , Argonne National Laboratory
[Host: Seunghun Lee]
ABSTRACT:
High Temperature Superconductors (HTSCs) were discovered more than 25 years ago. However, a microscopic theory of them is yet to be realized. In order to identify the mechanism behind superconductivity in these systems, we must understand the normal state from which superconductivity emerges. From our detailed Angle Resolved Photoemission Spectroscopy (ARPES) measurements on Bi2Sr2CaCu2O8+δ (BISCO 2212) HTSCs we have found that unlike conventional superconductors, where there is a single temperature scale Tc separating the normal from the superconducting state, HTSCs are associated with two additional temperature scales. One is the so-called pseudogap scale T*, below which electronic states are partially gapped, while the second one is the coherence scale Tcoh, characterizing the onset of a significant enhancement in electronic lifetime. We have observed that both T* and Tcoh change strongly with carrier concentration and they cross each other near optimal doping, i.e. the carrier concentration at which an HTSC attains its maximum Tc. Furthermore, there is an unusual phase in the normal state where the electronic excitations are gapped as well as coherent. Quite remarkably, this is the phase from which the superconductivity with maximum Tc emerges. Our experimental finding that T* and Tcoh intersect is not compatible with the theories invoking âsingle quantum criticalâ point near optimal doping, rather it is more naturally consistent with the theories of superconductivity for doped Mott insulators.
Colloquium
Thursday, January 26, 2012
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Putting the Genie Back in the Bottle: The Science of Nuclear Non-Proliferation"

Jerry Gilfoyle , University of Richmond
[Host: Simonetta Liuti]
SLIDESHOW:
Colloquium
Friday, January 20, 2012
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "How Green Can Algae Be? Alternative Energy from the Chesapeake Algae Project"

William Cooke , College of William and Mary
[Host: Tom Gallagher]
SLIDESHOW:
Colloquium
Friday, December 2, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Searching for Supersymmetry at the LHC"

Daniel Elvira , Fermi National Accelerator Lab
ABSTRACT:
Supersymmetry is a theory build under the hypothesis that there is a relation between bosons and fermions. The particle physics community finds it very compelling because it provides a solution to the mass hierarchy problem, allows a percent level unification of gauge couplings, and predicts a particle candidate for dark matter. The Large Hadron Collider (LHC) at CERN is the best instrument with count with at the moment to search for supersymmetric particles. It has delivered proton-proton collisions at a center of mass energy of 7 TeV since 2010. The CMS and ATLAS experiments at the LHC are expected to collect 4-5 fb-1 of data before the end of 2011 and explore a very significant fraction of the phase space associated with the most simple supersymmetric models. This talk will go over the experimental strategy for SUSY searches at the LHC, explain the techniques to evaluate the main backgrounds to potential SUSY signals, and review the most recent results.
SLIDESHOW:
Colloquium
Friday, November 18, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Peering into dark corners at Fermilab and CERN"

Bob Hirosky , University of Virginia
[Host: Joe Poon]
Colloquium
Monday, November 14, 2011
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Atomic calculations for tests of fundamental physics"

Marianna Safronova , University of Delaware
[Host: Kent Paschke]
ABSTRACT:
I will give an overview of applications of atomic calculations for atomic physics tests of fundamental physics, including the study of parity violation, search for EDM, and search for variation of fundamental constants. The goals of high-precision atomic parity violation (APV) studies are to search for new physics beyond the standard model of the electroweak interaction by accurate determination of the weak charge and to probe parity violation in the nucleus. I will discuss the current status and future prospects of atomic parity violation studies and the implications for searches for physics beyond the standard model. The recent advances in theoretical methodology that allowed to reduce theoretical uncertainty in the analysis of the cesium experiment are briefly outlined. I will also discuss recent accurate calculation of the nuclear spin-dependent parity-violating amplitude. New result still leads to the discrepancy between constraints on weak nucleon-nucleon coupling obtained from the cesium anapole moment and those obtained from other nuclear PV measurements.
SLIDESHOW:
Colloquium
Friday, November 11, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Nearly perfect fluidity: From cold atoms to hot quarks and gluons"

Thomas Schaefer , North Carolina State University
[Host: Peter Arnold]
ABSTRACT:
A dimensionless measure of fluidity is the ratio of shear viscosity to entropy density. In this talk we will argue that fluidity is a sensitive probe of the strength of correlations in a fluid. We will also discuss evidence that the two most perfect fluids ever observed are also the coldest and the hottest fluid ever created in the laboratory. The two fluids are cold atomic gases (~10^(-6) K) that can be probed in optical traps, and the quark gluon plasma (~10^{12} K) created in heavy ion collisions at RHIC (Relativistic Heavy Ion Collider at Brookhaven National Laboratory). Remarkably, both fluids come close to a bound on the shear viscosity that was first proposed based on calculations in string theory, involving non-equilibrium evolution of back holes in 5 (and more) dimensions.
SLIDESHOW:
Colloquium
Friday, November 4, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Electrons and Mirror Symmetry"

Kent Paschke , University of Virginia
[Host: Joe Poon]
SLIDESHOW:
Colloquium
Thursday, November 3, 2011
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "What Have We Learned from Electron Deep Inelastic Scattering?"

Xiaochao Zheng , University of Virginia
[Host: Joe Poon]
SLIDESHOW:
Colloquium
Monday, October 31, 2011
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Topological Insulators: From Fundamentals to Applications"

Di Xiao , Oak Ridge National Lab
[Host: Joe Poon]
ABSTRACT:
Topological insulators are materials that have a bulk band gap like an ordinary insulator but support protected conducting states on their edge or surface. These edge/surface states are predicted to have special properties that could be useful for applications ranging from spintronics to quantum computing. In this talk, I will explain the nontrivial band topology of these materials using the Berry phase concept, review current progress on material prediction and realization, and discuss some of the applications in surface catalysis and electronics.
Colloquium
Friday, October 28, 2011
4:00 PM
Physics Building, Room 204

## "Diving For Treasure In Complex Data "

Marvin Weinstein , Stanford University
[Host: Simonetta Liuti]
ABSTRACT:
All fields of scientific research have experienced an explosion of data. It is a formidable computational challenge to analyze this data to extract unexpected patterns. Meeting this challenge will require new, advanced methods of analysis. Dynamic Quantum Clustering is such a tool. The algorithm, invented by David Horn (Tel Aviv University) and myself, provides a highly visual and interactive tool that allows one to explore complicated data that has unknown structure. My talk will provide a brief introduction to the distinction between supervised and unsupervised methods in data mining (clustering in particular). Then, I will, very briefly, discuss the theory of DQC. The bulk of my talk will be devoted to showing results on a data set coming from the Stanford Synchrotron Radiation Laboratory and some results from data on earthquakes in the Middle East. These examples show the power of DQC applied to data sets on which the currently most favored unsupervised data mining techniques fail to obtain any interesting results. The message will be that large, complex, data sets typically exhibit extended structures that are significant and that cannot be seen by other methods.
SLIDESHOW:
Colloquium
Thursday, October 27, 2011
4:00 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Statistical mechanics and dynamics of multicomponent quantum gases"

Austen Lamacraft , University of Virginia
[Host: Joe Poon]
SLIDESHOW:
Colloquium
Wednesday, October 26, 2011
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

 RESERVED Colloquium Friday, October 21, 2011 4:00 PM Physics Building, Room 204  Add to your calendar

## "Antihydrogen Trapped"

Francis Robicheaux , Auburn University
[Host: Bob Jones]
ABSTRACT:
Atoms made of a particle and an antiparticle are unstable, usually surviving less than a microsecond. Antihydrogen, the bound state of an antiproton and a positron, is made entirely of antiparticles and is believed to be stable. It is this longevity that holds the promise of precision studies of matter-antimatter symmetry. Low energy (Kelvin scale) antihydrogen has been produced at CERN since 2002. I will describe the experiment which has recently succeeded in trapping antihydrogen in a cryogenic Penning trap for times up to approximately 15 minutes.
SLIDESHOW:
Colloquium
Friday, October 14, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Multi-Photon and Entangled-Photon Imaging and Lithography"

Malvin Teich , Boston University
[Host: Lauren Levac]
ABSTRACT:
Nonlinear optics, which governs the interaction of light with various media, offers a whole raft of useful applications in photonics, including multiphoton microscopy and multiphoton lithography. It also provides the physicist with a remarkable range of opportunities for generating light with interesting, novel, and potentially useful properties. As a particular example, entangled-photon beams generated via spontaneous optical parametric down-conversion exhibit unique quantum-correlation features and coherence properties that are of interest in a number of contexts, including imaging. Photons are emitted in pairs in an entangled quantum state, forming twin beams. Such light has found use, for example, in quantum optical coherence tomography, a quantum imaging technique that permits an object to be examined in section. Quantum entanglement endows this approach with a remarkable property: it is insensitive to the even-order dispersion inherent in the object, thereby increasing the resolution and section depth that can be attained. We discuss the advantages and disadvantages of a number of techniques in multiphoton and entangled-photon imaging and lithography.
SLIDESHOW:
Colloquium
Friday, October 7, 2011
4:00 PM
Physics Building, Room 204

Colloquium: Kickoff Event for The Optical Society of America at UVA

Slideshow (PDF)

## "The cultural and ethical world of nuclear weapons scientists"

Hugh Gusterson , George Mason University
[Host: Seunghun Lee]
ABSTRACT:
The Los Alamos and Lawrence Livermore National Laboratories are the two largest employers of physicists in the country. Their primary mission is nuclear weapons science. Based on over two decades studying the culture of nuclear weapons scientists as an anthropologist, the speaker discusses the values of nuclear weapons physicists, the reasons young physicists have for choosing a career in nuclear weapons design, the ethical challenges they confront, and the degree of job satisfaction they report.
SLIDESHOW:
Colloquium
Friday, September 30, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, September 23, 2011 4:00 PM Physics Building, Room 204  Add to your calendar

## "Electronic Detection and Diagnosis of Health and Illness of Premature Infants"

John Delos , College of William and Mary
[Host: Tom Gallagher]
ABSTRACT:
The pacemaking system of the heart is complex; a healthy heart constantly integrates and responds to extracardiac signals, resulting in highly complex heart rate patterns with a great deal of variability. In the laboratory and in some pathological or age related states, however, dynamics can show reduced complexity that is more readily described and modeled. Reduced heart rate complexity has both clinical and dynamical significance - it may provide warning of impending illness or clues about the dynamics of the heart's pacemaking system. Here we describe simple and interesting heart rate dynamics that we have observed in premature human infants - reversible transitions to large- amplitude periodic oscillations - and we show that they give early warning of bacterial infections in premature infants, and we show that the appearance and disappearance of these periodic oscillations can be described by a simple mathematical model, a Hopf bifurcation.
Colloquium
Friday, September 16, 2011
4:00 PM
Physics Building, Room 204

 Available Colloquium Friday, September 9, 2011 4:00 PM Physics Building, Room 204  Add to your calendar

## "Having your cake and seeing it too: In Situ Observation of Incompressible Mott Domains in Ultracold Atomic Gases"

Cheng Chin , University of Chicago
[Host: Seunghun Lee]
ABSTRACT:
Atoms at ultralow temperatures are fascinating quantum objects, which can tunnel through barriers, repel or attract each other, and interfere like electromagnetic waves. This wavy behavior of ultracold atoms evidently illustrates the particle-wave duality as discussed in modern physics. By loading repulsively interacting atoms into a regular array of tiny optical cells (called optical lattices), we show that the wavy nature of the atoms can be completely destroyed. At the same time, the gaseous sample develops an interesting multi-layer structure with quantize density plateaus, resembling a multi-tier wedding cake. Our observation of the cake structure in ultracold gases of atoms [1] raises new prospects to investigate the dynamics and transport across a phase boundary [2] and to identify universal critical behavior in the transition regime [3]. Surprising findings along these directions will be reported.
SLIDESHOW:
Colloquium
Friday, September 2, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 RESERVED Colloquium Friday, August 26, 2011 4:00 PM Physics Building, Room 204  Add to your calendar

## "Application of Machine Learning Methods to Genome-Wide Maps of Histone Methylations"

Stefan Bekiranov , UVA Medical School
[Host: Eugene Kolomeisky]
ABSTRACT:
The physical length of one copy of the human genome is a little over 1 meter. It is packaged into a nucleus, which is on the order of micrometers in diameter. This is achieved by wrapping the DNA around histones. In the last decade, many breakthroughs have lead to the understanding that these histones control subsets of genes that are turned on or off depending on chemical modifications on their tails. They accomplish this by controlling the accessibility of proteinsâresponsible for turning genes onâto DNA. This accessibility can be characterized by two states: open and closed. Remarkably, over 60 different locations on these tails are subject to at least one of eight types of chemical modifications. Recently, it has been shown that many of these modifications work together to robustly turn genes on or off; however, we are at the beginning of uncovering this complex control network. To shed light on this network, we apply computational methods, which identify statistically significant combinations, to genome wide maps of histone modifications. We indeed find that crosstalk among these modifications is extensive and predict novel combinations, which strongly synergize in our models, for further biochemical study.
SLIDESHOW:
Colloquium
Friday, April 29, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Physics professors Bob Jones, Olivier Pfister, Cass Sackett, and Steve Thornton will delight the crowd with strange and mystifying events."

A Family-Oriented Event ,
ABSTRACT:
See rockets shooting around the auditorium, balls suspended in air, curve balls flying overhead, Van de Graaff generators, skaters spinning around. You will see you a bunch of fascinating things you should never do at home. We might even put someone on a bed of nails and crush a cement block on top of them. As usual, there will be plenty of surprises in store. These demonstrations will intrigue and excite both young and old and from novice to expert. Bring your family and friends, but come on time. For more information about this free public event call 924-3781.
Colloquium
Wednesday, April 27, 2011
7:00 PM
Physics Building, Room 203

National Physics Day Show

## "The Quincunx Point"

Sylvester J. Gates , University of Maryland
[Host: Diana Vaman]
ABSTRACT:
Sometimes theoretical physics problems resist resolution for decades. Endeavoring to solve such problems can lead to a new and unexpected viewpoint. Prof. Gates will describe such a problem and describe how trying to solve it has possibly led to a quincunx point at the five-fold overlap of art, mathematics, music, science, and perhaps...
Colloquium
Friday, April 22, 2011
4:00 PM
Physics Building, Room 204

## "Elementary Particles of Superconductivity"

Assa Auerbach , Technion, Israel Institute of Technology
[Host: Israel Klich]
ABSTRACT:
Historically, two paradigms competed to explain superconductivity (i) Bose Einstein Condensation of weakly interacting Charge 2e pairs (Schafroth), and (ii) Pairing instability of the Fermi liquid (BCS). BCS theory was the unquestionable winner until the late 80's. BCS approximations however, have suffered major setbacks in the advent of high temperature, short coherence length superconductors, such as cuprates, pnictides, and granular superconducting films. A third paradigm has offered itself: Hard Core lattice Bosons (HCB), which are experimentally realized in cold atoms on optical lattices. HCB behave less like weakly interacting bosons or fermions, but (strangely) more like quantum spins. Their static correlations are very well understood by theories of quantum antiferromagnets. Recent calculations of the conductivity of Hard Core Bosons suggests a new route to understanding linear in temperature resistivity and other strange metallic properties above the transition temperature.
SLIDESHOW:
Colloquium
Friday, April 15, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 RESERVED Colloquium Friday, April 8, 2011 4:00 PM Physics Building, Room 204  Add to your calendar

## "Beyond Smoke and Mirrors: Climate Change and Energy in the 21st Century"

Burton Richter , Stanford University
ABSTRACT:

Professor Richter is the co-winner of the 1976 Nobel Prize in physics for the discovery of the J/Ψ particle which was the first observation of a particle containing a fourth quark named the charm quark and was a central part of the so-called November revolution of particle physics. He has accumulated many other honors in his career including a long tenure as the director of Stanford Linear Acceleratory Laboratory from 1984 to 1999. He has also been the recipient of the E.O. Lawrence Medal, has served as president of the American Physical Society, and is a member of the National Academy of Sciences. He presently serves on the board of directors of Scientists and Engineers for America, an organization focused on promoting sound science in American government and is a Senior Fellow by Courtesy of the Center for Environmental Science and Policy at Stanford Institute for International Studies. In the past several years Professor Richter has turned his attention to the central problem of the 21st century, the effect of human activity on the global climate. He has written a book with the same title as his lecture.

SLIDESHOW:
Colloquium
Thursday, April 7, 2011
7:00 PM
Chemistry , Room 402

Hoxton Lecture

Slideshow (PDF)

 Grad Poster Competition Colloquium Friday, April 1, 2011 4:00 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, March 25, 2011 4:00 PM Physics Building, Room 204  Add to your calendar
 Reserved Colloquium Friday, March 18, 2011 4:00 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, March 4, 2011 4:00 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, February 25, 2011 4:00 PM Physics Building, Room 204  Add to your calendar

## "Modern math in medieval islamic architecture"

Peter Lu , Harvard University
[Host: Peter Arnold]
ABSTRACT:
The conventional view holds that girih (geometric star-and-polygon) patterns in medieval Islamic architecture were conceived by their designers as a network of zigzagging lines, and drafted directly with a straightedge and a compass. I will describe recent findings that, by 1200 C.E., a conceptual breakthrough occurred in which girih patterns were reconceived as tessellations of a special set of equilateral polygons (girih tiles) decorated with lines. These girih tiles enabled the creation of increasingly complex periodic girih patterns, and by the 15th century, the tessellation approach was combined with self-similar transformations to construct nearly-perfect quasicrystalline patterns. Quasicrystal patterns have remarkable properties: they do not repeat periodically, and have special symmetry---and were not understood in the West until the 1970s. I will discuss some of the properties of Islamic quasicrystalline tilings, and their relation to the Penrose tiling, perhaps the best known quasicrystal pattern.
Colloquium
Friday, February 18, 2011
4:00 PM
Physics Building, Room 204

## "Supermassive Black Holes and the Evolution of Galaxies"

Jim Condon , NRAO
[Host: PQ Hung]
ABSTRACT:
The first galaxies were small condensations of baryonic matter that fell into the gravitational potentials of dark-matter halos, and larger galaxies are still being assembled from smaller ones by heirarchical merging. Black holes quickly formed and grew in their centers, and energy feedback from these supermassive black holes (SMBHs) dominated the subsequent growth and stellar composition of large galaxies, making them "red, dead, and elliptical" today. To constrain the role of SMBHs in galaxy evolution we recently measured accurate nuclear masses of six Seyfert galaxies using the Keplerian rotation curves of circumnuclear water masers observed with 0.0003 arcsec resolution. The nuclear mass densities are so high that they are consistent only with supermassive black holes, not dense star clusters. Because nearly all galaxies contain SMBHs, recently merged galaxies should contain inspiraling binary SMBHs that may merge and emit very energetic and anisotropic bursts of gravitational radiation. We recently began the first systematic search for inspiraling, binary, or recoiling SMBHs in hundreds of nearby massive galaxies.
SLIDESHOW:
Colloquium
Friday, February 11, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Top Quarks at the Large Hadron Collider: In Pursuit of Truth and its Consequences"

Chris Neu , University of Virginia
[Host: Joe Poon]
ABSTRACT:
The top quark is a unique member of the collection of known fundamental particles. Its mass is exceedingly large -- nearly that of a single atom of gold -- which is remarkable given that the top quark is considered to be a point particle with no substructure. Further, the top quark decays rapidly, long before having the chance to form a bound state with other quarks. Hence, the study of top-quark decays affords a direct glimpse at the properties of the parent quark itself, allowing measurements of its mass, spin, charge and other properties. Finally, several signatures of new phenomena accessible at particle colliders either suffer from top-quark production as a significant background or contain top quarks themselves. With the advent of the operational era of the Large Hadron Collider (LHC), the Compact Muon Solenoid (CMS) experiment has the opportunity to perform precision measurements of top-quark production and decay for the first time away from Fermilab's Tevatron collider, whose experiments produced the discovery of the top quark in 1994. In this talk I will present some of the first results of the CMS top-quark physics program, results in which members of the University of Virginia CMS group made significant contributions.
Colloquium
Tuesday, February 8, 2011
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Entanglement and Entropy in many body systems"

Israel Klich , University of Virginia
[Host: Joe Poon]
ABSTRACT:
As physical systems are cooled down, their properties may no longer be described in classical terms, and we enter a quantum regime. Perhaps the most fascinating quantum property is entanglement. Recently, with understanding of entanglement between a few particles, many-body entanglement has received great interest in such varied fields as condensed matter, cosmology and quantum information. Indeed, the scaling of entanglement in large systems is a sensitive measure of the nature of interactions and phases. In contrast with typical thermodynamical behavior, the entanglement entropy of a sub region in a physical system often grows as it's boundary area, and not as its volume. In this talk, I will describe such âarea lawsâ, their appearance and relation to quantum phase transitions. I will also discuss a yet more detailed analysis of such entanglement, known as entanglement spectrum. Finally, I will exhibit a universal relation between entanglement and statistics of current flowing through a quantum point contact, which provides a way to experimentally measure entanglement entropy.
Colloquium
Friday, February 4, 2011
4:00 PM
Physics Building, Room 204

## "Supersymmetry"

Stephen Martin , Northern Illinois University
ABSTRACT:
Supersymmetry is a proposed symmetry of particle physics that relates fermions and bosons to each other. It makes the exciting prediction that for every known elementary particle there is a heavier "superpartner" particle waiting to be discovered. One of these superpartners may be the dark matter required by astrophysical and cosmological observations. I will explain the motivations behind supersymmetry, the predicted properties of the superpartner particles, and review indirect evidence suggesting that at least some of them are likely to be discovered at the Large Hadron Collider within the next few years. Several of the most likely possibilities for the discovery signature for superpartners will be discussed.
SLIDESHOW:
Colloquium
Friday, January 28, 2011
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Memristance and Negative Differential Resistance in Transition Metal Oxides"

Stan Williams , HP
[Host: Stu Wolf]
ABSTRACT:
Memristive devices are nonlinear dynamical systems that exhibit continuous, reversible and nonvolatile resistance changes that depend on the polarity, magnitude and duration of an applied electric field. The memristive properties of metal/metal oxide/metal (MOM) materials systems were discovered in the 1960s and studied without reaching a consensus on the physical mechanism, while the theoretical foundation of memristance was derived by Chua in 1971 without realizing there were physical examples of this circuit property. Recent studies on the mechanism revealed that memristive switching is caused by electric field-driven motion of charged dopants that define the interface position between conducting and semiconducting regions of the film. There have also been multiple reports of current-controlled negative differential resistance (CC-NDR) in electroformed MOM devices since the early 1960s (e.g. oxides of V, Nb, Ta, Ti and Fe), and there have been a variety of proposals for the physical mechanism. Current work presents persuasive evidence that CC-NDR in these materials is due to a Joule-heating induced metal-insulator transition (MIT). We have found that both memristance and CC-NDR coexist in many transition metal oxides, and the fact that both effects have been called "switching" has caused a great deal of confusion in the literature and prevented comprehensive understanding of these systems. I will explain the origin of both effects in titanium oxides and show some potential applications of combining the two effects in a single nanoscale device.
Colloquium
Friday, January 21, 2011
4:00 PM
Physics Building, Room 204

## "Sport Science and the Perfection Point"

John Brenkus , ESPN
[Host: Lou Bloomfield]
ABSTRACT:
UVA alum John Brenkus will talk about the science of sport, drawing upon his vast experience as the creator, executive producer, and host of the Emmy Award-winning show âSport Scienceâ on ESPN. He will also discuss his recent book "The Perfection Point," which debuted at #1 on BarnesAndNoble.com when it was released on September 1. On âSport Science,â Brenkus has the top athletes on the planet into his state-of-the-art laboratory to uncover sportsâ biggest myths and mysteries by using cutting-edge technology to measure momentum, friction and the laws of gravity (Sport Science website). Brenkus often wires himself up and steps in the line of fire against pro athletes to see how a ânormalâ guy stacks up against the pros (human crash-test dummy video).
Colloquium
Friday, December 3, 2010
4:00 PM
Physics Building, Room 204

## "Status of LHCb Experiment"

Tomasz Skwarnicki , Syracuse University
ABSTRACT:
LHCb experiment is dedicated to searches for new forces in decays of heavy flavors. I will give an introduction to its physics program. I will discuss the detector performance as measured on the first data, present first results and make projections to near and further future.
SLIDESHOW:
Colloquium
Friday, November 19, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "CaF: Just Large Enough, and Ca: Even Smaller"

Robert Field , MIT
[Host: Tom Gallagher]
ABSTRACT:
CaF is as ânot-atomâ as a diatomic molecule can be. The core-penetrating and core-nonpenetrating Rydberg states of CaF are observed by two-color Resonance Enhanced Ionization spectroscopy. The observed rovibronic energy levels are input to an energy- and internuclear distance-dependent Multichannel Quantum Defect Theory fit model. The fitted quantum defect matrix, μ(E,R), accounts for nearly all spectra and dynamics of CaF. A âzone of deathâ is observed, where selection-rule-shattering âindirectâ interactions of all Rydberg states with each other, is caused by one repulsive electronic potential curve. A STIRAP-like, multiphoton, chirped pulse, millimeter wave scheme for âjumping overâ this zone of death is being developed. Progress toward âpure electronic spectroscopyâ and magnetic resonance-like manipulation of molecular Rydberg states requires taking a step that Arthur Schawlow would have liked, back from CaF, with its one atom too many, to the Ca atom. 5 kilo-Debye Rydberg-Rydberg transitions in Ca are directly detected by Free Induction Decay signals, rather than indirectly, via ions or UV fluorescence, in a pulsed supersonic jet.
SLIDESHOW:
Colloquium
Friday, November 12, 2010
4:00 PM
Physics Building, Room 204

Joint Chemistry-Physics Colloquium

Slideshow (PDF)

## "GEM*STAR (Green Energy-Multiplier: Sub-critical, Thermal spectrum, Accelerator-driven, Recycling Reactor)"

Bruce Vogelaar , Virginia Tech
[Host: Blaine Norum]
ABSTRACT:
The world faces serious energy issues, and while nuclear energy could in principle address base-line needs, current methods intrinsically link it to proliferation, waste, high-construction cost, and safety issues. Advances (as confirmed in the 2010 Department of Energy study) in accelerator technology (e.g. SRF at JLab) now allow neutrons to be reliably generated at low-enough cost that a reactor core with a critical mass of fissile material is no longer required. The combination obviates the historical incremental approach to nuclear energy being pursued in this country.

The GEM*STAR approach to such an Accelerator Driven System (ADS) thus intrinsically breaks the links to issues which have crippled the nuclear energy option. It does this by requiring: no enrichment, no reprocessing, no critical-mass on site; and providing far deeper burning with orders-of-magnitude less releasable radioactivity in its core and resulting in far less final waste. The project will demonstrate electricity cheaper than coal, and could beneficially utilize today's LWR spent fuel producing no additional waste.

Results from the recent workshop on ADS (hosted by VT and JLab) along with the new report from the DOE will be presented. GEM*STAR is a project of ADNA Corp. and the Virginia GEM*STAR Consortium (VCU, VT, JLab, UVA).
SLIDESHOW:
Colloquium
Friday, November 5, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Quantum computing over the rainbow"

Olivier Pfister , University of Virginia
[Host: Joe Poon]
ABSTRACT:
Quantum computing has attracted much attention over the past sesquidecade because it makes integer-factoring easy, even though that has been a historically (if not provably) hard mathematical problem [1]. Another major interest is the exponential speedup of quantum simulations [2]. The physical implementation of nontrivial quantum computing is an exciting, if daunting, experimental challenge, epitomized by the issues of decoherence and scalability of the quantum registers and processors. In this talk, I will present a novel scheme for realizing a scalable quantum register of potentially very large size, entangled in a "cluster" state, in a remarkably compact physical system: the optical frequency comb (OFC) defined by the eigenmodes of a single optical resonator. The classical OFC is well known as implemented by the femtosecond, carrier-envelope-phase- and mode-locked lasers which have redefined time/frequency metrology and ultraprecise measurements in recent years [3,4]. The quantum version of the OFC is then a set of harmonic oscillators, or "Qmodes," whose amplitude and phase are analogues of the position and momentum mechanical observables. The quantum manipulation of these continuous variables for one or two Qmodes is a mature field. Recently, we have shown theoretically that the nonlinear optical medium of a single optical parametric oscillator (OPO) can be engineered, in a sophisticated but already demonstrated manner, so as to entangle, in constant time, the OPO's OFC into a cluster state of arbitrary size, suitable for one-way quantum computing over continuous variables [5,6]. I will describe the mathematical proof of this result and report on our progress towards its experimental implementation at the University of Virginia.

[1] P. W. Shor, âAlgorithms for quantum computation: discrete logarithms and factoring,â in Proceedings, 35th Annual Symposium on Foundations of Computer Science, S. Goldwasser, ed., pp. 124â134 (IEEE Press, Los Alamitos, CA, Santa Fe, NM, 1994).

[2] R. P. Feynman, âSimulating Physics With Computers,â Int. J. Theor. Phys. 21, 467 (1982).

[3] J. L. Hall, âNobel Lecture: Defining and measuring optical frequencies,â Rev. Mod. Phys. 78, 1279 (2006)

[4] T. W. HÃ¤nsch, âNobel Lecture: Passion for precision,â Rev. Mod. Phys. 78, 1297 (2006).

[5] N. C. Menicucci, S. T. Flammia, and O. Pfister, âOne-way quantum computing in the optical frequency comb,â Phys. Rev. Lett. 101, 130501 (2008).

[6] S. T. Flammia, N. C. Menicucci, and O. Pfister, âThe optical frequency comb as a one-way quantum computer,â J. Phys. B, 42, 114009 (2009).

Colloquium
Friday, October 29, 2010
4:00 PM
Physics Building, Room 204

 Available Colloquium Friday, October 22, 2010 4:00 PM Physics Building, Room 204  Add to your calendar

## "Exploring the Universe with Gamma-Rays"

Brian Winer , Ohio State University
[Host: Chris Neu ]
ABSTRACT:
The most energetic phenomena in the cosmos are often revealed through their gamma-ray emissions. Observing gamma-rays up to ~100 GeV requires a space-born observatory. The Fermi Gamma-Ray Space Telescope (FGST) was launched in June 2008 and is beginning its third year of observation of a mission that will last at least 5 years. The primary instrument on FGST is the Large Area Telescope (LAT), which is sensitive to gamma rays from ~20 MeV to over 300 GeV. The current status of the Fermi mission will be discussed along with results from a variety of astrophysical topics including the search for indirect evidence of dark matter.
Colloquium
Friday, October 15, 2010
4:00 PM
Physics Building, Room 204

## "Materials world under scrutiny: the view using a very powerful probe"

Despina Louca , University of Virginia
[Host: Joe Poon]
ABSTRACT:
The emergence of unique physical properties in solids is a manifestation of the coexistence and competition of several degrees of freedom. They are probed by neutrons which provide details on the structure and dynamics. Examples of systems that will be discussed include the magnetoresistive perovskite oxides, bulk metallic alloys, and the new class of superconductors. Understanding the macroscopic functionality of these systems can be potentially very useful for industrial applications.
Colloquium
Friday, October 8, 2010
4:00 PM
Physics Building, Room 204

## "Science, Political Science, and Social Responsibility"

J.J. Suh and Seunghun Lee , Johns Hopkins University / University of Virginia
[Host: Seunghun Lee]
ABSTRACT:
J.J. Suh, a political scientist, and S.-H. Lee, a physicist, have been working together to find out what really happened to the South Korean (SK) Navy corvette, the Cheonan, that sank on March 26, 2010 in the Yellow Sea near the sea border with North Korea. On May 20 after almost two months of investigation, the SK-appointed Joint Investigation Group concluded that the Cheonan had been destroyed by a North Korean torpedo. Our close examination of the JIG's evidence, however, shows that its conclusion is scientifically untenable and that the integrity of some of its scientific data has been compromised. This episode clearly illustrates the need of interaction and collaboration between social science and natural science experts when science gets entangled with politics, as it often does in this technologically ever-developing world.
SLIDESHOW:
Colloquium
Friday, October 1, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "The Jefferson Lab Program on Inclusive and Semi-Inclusive Deep Inelastic Scattering"

Sebastian Kuhn , Old Dominion University
[Host: Don Crabb]
ABSTRACT:
Nucleons (protons and neutrons) play a dual role as the building blocks of atomic nuclei (which constitute nearly all of the mass visible around us) and as stable systems bound by the fundamental strong force of Quantum ChromoDynamics (QCD). When studied with the most powerful microscopes (accelerators) on Earth, nucleons appear as a chaotic jumble of a nearly infinite number of “partons” (quarks, antiquarks and gluons). However, at the more moderate resolution available at Jefferson Lab, a simpler picture emerges: the quantum numbers of the nucleon are due to just three “valence” quarks which carry a large fraction of its energy-momentum, plus a few quark-antiquark pairs and gluons. One of the main research programs at Jefferson Lab is a detailed study of the distribution in space and momentum space of these partons, and their intrinsic spins. Deep inelastic scattering (DIS), where a relatively large momentum and energy is transferred from a scattered electron to the struck nucleon, is a primary tool to unravel this “medium resolution” structure of the nucleon. Additional information becomes available when one detects part of the final-state debris as well as the scattered electron (semi-inclusive DIS). In my talk, I will give some examples of experiments at Jefferson Lab that employ these tools, and explain what we can learn from them.
Colloquium
Friday, September 24, 2010
4:00 PM
Physics Building, Room 204

 Available Colloquium Friday, September 17, 2010 4:00 PM Physics Building, Room 204  Add to your calendar

## "Beauty is only skin deep; probing thin film and membrane structure by neutron reflection"

Chuck Majkrzak , NIST
[Host: Seunghun Lee]
ABSTRACT:
Over the course of the last two decades, neutron reflectometry has become established as an important structural probe of thin films and multilayered composites, most notably of hydrogenous and magnetic materials. As an introduction, the basic principles and typical applications of neutron reflectometry are briefly reviewed. Examples of neutron reflectometry studies of thin film systems of interest in condensed matter physics, chemical physics, and biophysics are presented. In particular, the scattering length density (SLD) depth profile along the surface normal, averaged over in plane, can be deduced from specular neutron reflectivity measurements (wavevector transfer Q normal to the surface). The SLD profile, in turn, is directly related to the corresponding material composition distribution. Under favorable conditions, specular neutron reflectometry can resolve variations in the compositional depth profile on a length scale of the order of a nanometer for a thin film having a single unit repeat, whereas for a periodic multilayered system, the spatial resolution can approach an Angstrom. For specular neutron reflection, the complex reflection amplitude or phase associated with an "unknown" segment of a composite film structure can be determined exactly, using reference segments, and a subsequent direct inversion can be performed, thereby ensuring, in principle, a unique result [1]. Thus, the phasesensitive neutron reflection / inversion process results in a realspace picture without fitting or any adjustable parameters. We will discuss how, because of the onetoone correspondence between the complex reflection amplitude and the SLD, phasesensitive NR can be viewed, in effect, as being equivalent to a realspace imaging process one in which the inversion computation plays an analogous role to that of the brain, for instance, in interpreting the optical image of an object focused on the retina of the eye [2]. In performing phasesensitive reflectivity measurements in practice, what ultimately limits the accuracy and spatial resolution of the depth profile are the maximum range of Q attainable and the statistical uncertainty in the measured reflected intensities. These effects can be analyzed quantitatively [3] and we will consider the spatial resolution currently possible as well as what can be reasonably expected in the future with more advanced neutron sources and instrumentation (e.g., employing polychromatic beams at continuous sources). Finally, we will critically examine a possible alternative approach to performing neutron reflectivity measurements, which involves the quantum phenomenon of "Interaction Free Measurement" (IFM) of the type first proposed by Dicke [4] and realized in rudimentary fashion by Kwiat et al. with visible light [5]. The scheme utilized by Kwiat et al. purportedly optimizes the efficiency for performing an IFM of the reflectivity (or transmission) by application of the quantum Zeno effect (which requires polarized photons or neutrons) within an interferometer.
SLIDESHOW:
Colloquium
Friday, September 10, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, September 3, 2010 4:00 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, August 27, 2010 4:00 PM Physics Building, Room 204  Add to your calendar

## "The Search for the Heisenberg-Schwinger Effect: Nonperturbative Pair Production from Vacuum"

Gerald Dunne , University of Connecticut
[Host: Israel Klich]
ABSTRACT:
The Heisenberg-Schwinger effect is the non-perturbative production of electron-positron pairs when an external electric field is applied to the quantum electrodynamical (QED) vacuum. The inherent instability of the quantum vacuum in an electric field was one of the first non- trivial predictions of QED, but the effect is so weak that it has not yet been directly observed. However, new developments in ultra-high intensity lasers come tantalizingly close to opening a new window on this unexplored extreme ultra-relativistic regime. This necessitates a fresh look at both experimental and theoretical aspects of the Heisenberg-Schwinger effect. I review the basic physics of the problem and describe some recent theoretical ideas aimed at making this elusive effect observable, by careful shaping of laser pulses. This is an example of an emerging new field using ultra-intense lasers to probe fundamental problems in particle physics, gravity and quantum field theory.
Colloquium
Friday, April 30, 2010
4:00 PM
Physics Building, Room 204

 Available Colloquium Friday, April 23, 2010 4:00 PM Physics Building, Room 204  Add to your calendar

## "Applied string theory -- from gravitational collapse to quark-gluon liquids"

Paul Chesler , M.I.T.
[Host: Peter Arnold]
ABSTRACT:
A remarkable result from heavy ion collisions at the Relativistic Heavy Ion Collider is that shortly after a collision, the medium produced behaves as a nearly ideal liquid. The system is very dynamic and evolves from a state of two colliding nuclei to a liquid in a time roughly equivalent to the time it takes light to cross a proton. Understanding the mechanisms behind the rapid approach to a liquid state is a challenging task. In recent years string theory has emerged as a powerful tool to study non-equilibrium phenomena, mapping the (challenging) dynamics of quantum systems onto the dynamics of classical gravitational systems. The creation of a liquid in a quantum theory maps onto the classical process of gravitational collapse and black hole formation. I will describe how one can use techniques borrowed from numerical relativity in astrophysics to study processes which mimic the dynamics of heavy ion collisions.
Colloquium
Friday, April 16, 2010
4:00 PM
Physics Building, Room 204

 Available Colloquium Friday, April 9, 2010 4:00 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, April 2, 2010 4:00 PM Physics Building, Room 204  Add to your calendar

## "Casimir effect due to a single boundary as a manifestation of the Weyl problem"

Genya Kolomeisky , University of Virginia
[Host: Dinko Pocanic]
ABSTRACT:
The Casimir self-energy of a boundary is ultraviolet-divergent. In many cases the divergences can be eliminated by methods such as zeta- function regularization or through physical arguments (ultraviolet transparency of the boundary would provide a cutoff). Using the example of a massless scalar field theory with a Dirichlet boundary we explore the relationship between such approaches, with the goal of better understanding the origin of the divergences. We are guided by the insight due to Dowker and Kennedy (1978) and Deutsch and Candelas (1979), that the divergences represent measurable effects that can be interpreted with the aid of the theory of the asymptotic distribution of eigenvalues of the Laplacian first discussed by Weyl. In many cases the Casimir self-energy is the sum of cutoff-dependent (Weyl) terms having geometrical origin, and an "intrinsic" term that is independent of the cutoff. The Weyl terms make a measurable contribution to the physical situation even when regularization methods succeed in isolating the intrinsic part. Regularization methods fail when the Weyl terms and intrinsic parts of the Casimir effect cannot be clearly separated. Specifically, we demonstrate that the Casimir self-energy of a smooth boundary in two dimensions is a sum of two Weyl terms (exhibiting quadratic and logarithmic cutoff dependence), a geometrical term that is independent of cutoff, and a non-geometrical intrinsic term. As by-products we resolve the puzzle of the divergent Casimir force on a ring and correct the sign of the coefficient of linear tension of the Dirichlet line predicted in earlier treatments.
SLIDESHOW:
Colloquium
Friday, March 26, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Particle Physics â The Exciting Times at Fermilab"

Rob Roser , FNAL
[Host: Chris Neu]
ABSTRACT:
There has never been a more exciting time in Particle Physics. The Tevatron scientists are currently mining huge data samples and expect to double the sample yet again before the current run is through. Meanwhile, the intensity frontier effort is ramping up as Fermilab readies itself for life beyond the energy frontier. In my talk, I will discuss some of the exciting physics results that are currently coming out of the Tevatron program and discuss the future plans of the lab
SLIDESHOW:
Colloquium
Friday, March 19, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "The Race for the Higgs Boson(A Tevatron Perspective)"

R. Craig Group , Fermilab
[Host: Craig Dukes]
ABSTRACT:
I will begin by motivating the Higgs boson as an important piece of the Standard Model of particle physics that has yet to be experimentally verified. I will then give a short review of high energy colliders and particle detectors and will describe the challenges of discovering a Higgs boson with these machines. I will summarize the status at the Tevatron Collider at Fermilab and the Large Hadron Collider at CERN and portray the excitement at these two labs as the race to discover the Higgs boson tightens up.
SLIDESHOW:
Colloquium
Friday, March 5, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Low-Background Searches for Rare Events: The MAJORANA Neutrinoless Double-Beta Decay Experiment, and the CLEAN/DEAP Dark Matter Search"

Victor Gehman , Los Alamos National Laboratory
[Host: Craig Dukes]
ABSTRACT:
Rare event searches will have a profound impact on the search for physics beyond the Standard Model in the coming years. This is particularly true in searches for neutrinoless double-beta decay and dark matter, and we will discuss one experiment of each type. The MAJORANA experiment will search for neutrinoless double-beta decay in 76Ge by constructing an array of HPGe detectors in ultra-clean electro-formed copper cryostats deep underground. Recent advances in HPGe detector technology, particularly the development of P-type Point Contact (PPC) detectors present excellent new opportunities in identifying and reducing backgrounds to the double-beta decay signal. The CLEAN/DEAP collaboration is fielding MiniCLEAN, a 400-kg, single-phase detector capable of being filled with either liquid neon or argon. MiniCLEAN uses a spherical geometry to maximize light yield and pulse shape analysis techniques to identify nuclear recoil signals and reject electron recoil backgrounds. Careful attention is being paid to reducing the contamination of detector surfaces by environmental radon gas. We will present an overview and highlight recent R&D progress of both experimental programs.
SLIDESHOW:
Colloquium
Monday, March 1, 2010
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Dark Energy: Taking Sides"

Rocky Kolb , University of Chicago
[Host: Peter Arnold]
ABSTRACT:
Dark energy appears to be the dominant component of the present mass-density of the Universe, yet there is no persuasive theoretical explanation for its existence or magnitude. While the simplest explanation might be Einstein's cosmological constant, there are other possibilities, including dynamical dark energy, modification of general relativity, or back reactions of inhomogeneities. After framing the dark-energy problem, I will discuss possible theoretical solutions, as well as an observational program to study the properties of dark energy.
SLIDESHOW:
Colloquium
Friday, February 26, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "The MuLan Experiment: Measuring the Muon Lifetime to 1ppm"

Kevin Lynch , Boston University
[Host: Craig Dukes]
ABSTRACT:
The Standard Model of Particle and Nuclear physics makes thousands of successful predictions, based on roughly 20 experimentally determined input parameters. Studies on the Electroweak frontier in particular require extremely precise values for a subset of those parameters, including the Fermi Constant. I will describe the MuLan experiment, which has measured the muon lifetime with unprecedented part per million accuracy, improving our knowledge of the Fermi Constant by a factor of 20. I will describe the physics motivation for the measurement, emphasize the subtle design and analysis challenges of a measurement on the precision frontier, and discuss both our published results and current progress towards our ultimate physics goals.
SLIDESHOW:
Colloquium
Wednesday, February 24, 2010
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

## "Entering an Era of Precision Neutrino Physics"

Mitchell Soderberg , Yale University
ABSTRACT:
The discovery just over a decade ago that neutrinos can change identities by oscillating between flavors was a revolutionary change to the Standard Model description of particle physics. This discovery implies that neutrinos are not massless, and that they could play a crucial role in answering some of the most fundamental questions in particle physics, such as whether the observed matter-antimatter asymmetry in the universe can be attributed to CP violating neutrino interactions. Many experiments are currently attempting to solve the remaining mysteries of neutrino behavior, but this is a challenging task due to the elusive nature of these particles. Liquid Argon Time Projection Chambers (LAr TPCs) are ideally suited for the study of neutrino interactions thanks to their precision detection capabilities that make them the modern day equivalent of bubble chambers. In this talk I will motivate the compelling questions in neutrino physics and introduce the LAr TPC technique, highlighting recent work in the development of this technology, including discussion of the ArgoNeuT (Argon Neutrino Test) test-beam project and the MicroBooNE experiment. Finally, I will discuss preliminary ideas for the ultimate experiment that could be conducted at the Deep Underground Science and Engineering Laboratory (DUSEL) in South Dakota as part of a world-class U.S. neutrino program that is currently being planned.
SLIDESHOW:
Colloquium
Tuesday, February 23, 2010
3:30 PM
Physics Building, Room 204

Special Colloquium

Slideshow (PDF)

 Available Colloquium Friday, February 19, 2010 4:00 PM Physics Building, Room 204  Add to your calendar

## "Searches for a Standard Model Higgs Boson at the Collider Detector at Fermilab"

Jennifer Pursley , University of Wisconsin
[Host: Craig Dukes]
ABSTRACT:
In the standard model of particle physics, the Higgs mechanism is theorized to explain the broken symmetry of the electromagnetic and weak forces by giving mass to the W and Z gauge bosons. One consequence of this theory is the existence of another massive elementary particle, called the Higgs boson. While this theory of electroweak symmetry breaking was first introduced in the 1960's, the Higgs boson has yet to be observed experimentally and the theory remains unproven. Finding the Higgs boson is currently one of the primary goals of the Fermilab Tevatron collider and the Large Hadron Collider at CERN. In this colloquium I will start with a brief overview of the standard model of particle physics, the role played by the Higgs mechanism, and previous searches for a Higgs boson. Then I will introduce the Fermilab particle accelerator complex and the Collider Detector at Fermilab experiment, and discuss my own research searching for this elusive piece of the standard model. My focus is on the search for a high-mass Higgs boson, which primarily decays to two W bosons. Although we have not yet discovered a Higgs boson, at the Tevatron we are narrowing the possibilities. Within a few years we should know whether the standard model Higgs boson exists, or if we need a new solution.
Colloquium
Wednesday, February 17, 2010
3:30 PM
Physics Building, Room 204

Special Colloquium

## "Novel magnetism in ultracold atomic gases"

Austen Lamacraft , University of Virginia
[Host: Dinko Pocanic]
SLIDESHOW:
Colloquium
Friday, February 12, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Strings and QCD"

Diana Vaman , University of Virginia
[Host: Dinko Pocanic]
SLIDESHOW:
Colloquium
Friday, January 29, 2010
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "QCD in five dimensions"

Chris Dawson , University of Virginia
[Host: Dinko Pocanic]
SLIDESHOW:
Colloquium
Wednesday, January 27, 2010
3:30 PM
Physics Building, Room 204

Slideshow (PDF)

## "Why does the (free) neutron decay (?)"

Stefan Baessler , University of Virginia
[Host: Dinko Pocanic]
Colloquium
Friday, January 22, 2010
4:00 PM
Physics Building, Room 204

## "Meeting Future Energy Demand Through Unconventional Technology "

Kambiz Safinya , Schlumberger Research
[Host: Tom Gallagher]
ABSTRACT:
Crude oil production forecasts point to a drop of 40 M b/d of conventional oil by 2030. Although the financial and economic crisis has driven global energy lower in 2009 for the first time since 1981 on any significant scale, demand will resume its long-term upward trend once the economic recovery gathers pace. By 2030, world primary energy demand is forecast to be around 45% higher than today â this is like adding two more United States to world consumption. There is therefore a drive to develop alternative energy sources as well as unconventional hydrocarbon reserves to replace the lost production from conventional reservoirs. Given that conservative estimates of Heavy Oil reserves approach 6 trillion barrels, and that heavy oil production today is approaching 10% of world production, it is reasonable to suppose that a significant percentage of the production shortfall would be filled through the production of heavy oil. These facts and the significant increase in average crude oil price since the turn of the century have led to an increased level of interest in these types of reservoirs. It is also true that due to the nature of heavy oil, while the reserves are significant, the recoverable reserves are around 5%-7%. The challenge is therefore to develop technologies that can significantly increase the recovery factors of heavy oil reservoirs in an environmentally acceptable manner. This talk will focus on the current approach adopted by industry and the technologies which will be required to address the challenges stated here.
Colloquium
Friday, December 4, 2009
4:00 PM
Physics Building, Room 204

 RESERVED Colloquium Friday, November 20, 2009 4:00 PM Physics Building, Room 204  Add to your calendar

## "Nondispersing Rydberg Wavepackets"

Tom Gallagher , University of Virginia
[Host: Seunghun Lee]
ABSTRACT:
As first pointed out by Schrodinger, it is possible to make a "classical" atom, one in which the electron moves in an orbit around the nucleus, by creating superpositions of stationary quantum eigenstates. In quantum terms the probability has a moving spatial maximum. The idea lay dormant until the mode locked laser allowed the creation of atomic (and molecular) wavepackets. Such wavepackets usually disperse, that is, they lose their spatial localization after a few orbits. Dispersion can be prevented by applying an weak microwave field at the orbital frequency. The microwave field phase locks the electron's orbital motion, and by altering the microwave field it is possible to alter the electron's orbit. For example, increasing or decreasing the microwave frequency increases the orbital frequency, and changing the microwave polarization from linear to circular produces a circular orbit.
SLIDESHOW:
Colloquium
Friday, November 13, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Detecting Gravitational Waves (and doing other cool physics) with Millisecond Pulsars"

Scott Ransom , NRAO
[Host: PQ Hung]
ABSTRACT:
The first millisecond pulsar was discovered in 1982. Since that time their use as highly-accurate celestial clocks has improved continually, so that they are now regularly used to measure a variety of general relativistic effects and probe a variety of topics in basic physics, such as the equation of state of matter at supra-nuclear densities. One of their most exciting uses though, is the current North American (NANOGrav) and international (the International Pulsar Timing Array) efforts to directly detect nanohertz frequency gravitational waves, most likely originating from the ensemble of supermassive black hole binaries scattered throughout the universe. In this talk I'll describe how we are using an ensemble of pulsars to try to make such a measurement, how we could make a detection within the next 5-10 years, and how we get a wide variety of very interesting secondary science from the pulsars in the meantime.
SLIDESHOW:
Colloquium
Friday, November 6, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Nonequilibrium thermodynamics at the microscale"

Christopher Jarzynski , Univ. of Maryland
[Host: Austen Lamacraft]
SLIDESHOW:
Colloquium
Friday, October 30, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Nanotube & Graphite based electronics"

Keith Williams , University of Virginia
[Host: Dinko Pocanic]
SLIDESHOW:
Colloquium
Friday, October 23, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Entropy in Quantum Information Theory and Condensed Matter Physics"

Matthew Hastings , Station Q, UCSB
[Host: Israel Klich]
ABSTRACT:
While entropy was introduced in thermodynamics to describe heat engines, its applications have spread to widely different areas. I will talk about recent research on two such problems. The first is a problem in information theory: how much information can we send over a noisy communication channel, given that the world is described by quantum mechanics? I will explain the so-called "additivity conjecture", which was a proposed way to calculate the communication capacity of such a channel, and I will explain my recent result disproving this conjecture, showing that we can use entanglement to boost communication capacity. The second problem is in quantum systems far from equilbrium. Here I will describe how entropy can arise from quantum entanglement, and I will discuss novel simulation algorithms and future experiments probing the relaxation back to local thermal equilibrium.
SLIDESHOW:
Colloquium
Friday, October 16, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Energy: No Such Thing as a Free Lunch"

Eric Prebys , Fermilab
[Host: Craig Dukes]
ABSTRACT:
Mankind has had a long obsession with the quest for limitless or virtually limitless sources of energy. This quest did not stop with the advent of modern physics, but much of it moved out of the realm of science and into the realm of pseudo-science. Today, "free energy" is a thriving, multi-million dollar business. It involves a colorful cast of characters that range from the sincerely self-deluded to outright charlatans. The fact their claims are given greeted with such credulity by both the public and the news media has profound implications about the general state of scientific understanding in our society.
SLIDESHOW:
Colloquium
Friday, October 9, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, October 2, 2009 4:00 PM Physics Building, Room 204  Add to your calendar

## "Dark Energy and the Hubble Constant"

Jim Condon , NRAO
[Host: PQ Hung]
ABSTRACT:
Dark energy dominates the expansion of the universe and will determine its ultimate fate. The best complement to cosmic microwave background data for constraining the nature of dark energy is an accurate measurement of the current expansion rate (Hubble constant). The goal of the Megamaser Cosmology Project is to measure the Hubble constant by using the Green Bank Telescope and the Very Long Baseline Array to discover and image 22 GHz water masers orbiting the nuclei of Seyfert galaxies. We can show that these compact nuclei contain supermassive black holes, not just dense clusters of stars, and determine their masses. In the past year we improved our measurement of the angular-size distance to the galaxy UGC 3789, imaged four more masing galaxies, and derived a preliminary estimate for the Hubble constant.
SLIDESHOW:
Colloquium
Friday, September 25, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Exploring the Nature of Matter: Jefferson Lab and its plans"

Hugh Montgomery , Director of JLab
[Host: Gordon Cates]
ABSTRACT:
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of the premier facilities for nuclear and hadronic physics in the world. With high luminosity and high polarization continuous wave electron beams, the 6 GeV physics program has produced exciting results during the past decade. Currently the laboratory is executing an upgrade of the accelerator from 6 GeV to 12 GeV: this project was recommended as the top priority in the most recent US nuclear physics long-range plan. The upgrade, which also includes changes to the experimental facilities, will open new avenues of investigation. Beyond this upgrade Jefferson Lab is preparing the case for a future Electron Ion Collider.
SLIDESHOW:
Colloquium
Friday, September 18, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, September 11, 2009 4:00 PM Physics Building, Room 204  Add to your calendar

## " E = mc^2, High energy and intensity opens windows on the world"

Young-kee Kim , Deputy Director, Fermilab/University of Chicago
[Host: Seunghun Lee]
ABSTRACT:
The profound discovery of Einstein a century ago, that particles can both be made from energy and disappear back into energy, inspires the experiments that provide our knowledge of the smallest building blocks of matter. The experiments, done at enormous energy and intensity frontier accelerators, have led to a consistent theory of the origins of our world up to a certain point. However, at an energy scale not far above what we can attain at existing accelerators, this picture is predicted to break down. Moreover, the theory of the very small is intimately connected to cosmology -- the ultimate cause and structure of our universe. Cosmological observations again point to the need for a new theory in this energy range. In this colloquium, I will trace out the path from where we are and what we need to do to take the next step towards understanding the nature of space and time. The discovery of new particles or new laws at energy and intensity frontier accelerators will open up windows on this world.
SLIDESHOW:
Colloquium
Friday, September 4, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, August 28, 2009 4:00 PM Physics Building, Room 204  Add to your calendar

## "Superconductivity at the Dawn of the Iron Age"

Zlatko Tesanovic , Johns Hopkins University
[Host: Seunghun Lee]
ABSTRACT:
Recent discovery of iron-based high temperature superconductors hints at a new pathway to the room temperature superconductivity. The new materials feature FeAs layers instead of the signature CuO2 planes of much-studied cuprate superconductors. The antiferromagnetism also appears to be involved, although the d-electrons in FeAs seem considerably more mobile than their cuprate cousins. This high mobility, facilitated by a large overlap between atomic orbitals of Fe and As, plays a crucial role in warding off Hund's rule and the large local moment magnetism of Fe ions, the archrival of superconductivity. I will present a pedagogical review of the current status of the field, highlighting similarities and differences between iron pnictides and cuprates, and emphasizing the importance of the multiband nature of magnetism and superconductivity in these new materials.
Colloquium
Friday, May 1, 2009
4:00 PM
Physics Building, Room 204

## "Academic Fraud and a Calculus of Death"

George Gollin , University of Illinois
[Host: Craig Dukes ]
ABSTRACT:
For a price, it is possible to acquire unearned academic degrees from non-existent universities that market diplomas over the internet. The most sophisticated of these diploma mill cartels, based in Spokane, Washington, used the turmoil in Western Africa to foster the illusion of recognition and accreditation by the Republic of Liberia. But these credentials were obtained through payments to government officials, and were no more legitimate than the supporting web of fake diplomatic missions, schools, accreditors, and credential evaluators created by the "Saint Regis University" group. Their operation spanned at least eighteen states and twenty-two countries, and their stable of degree mills included over seventy non-existent schools selling degrees in medicine, nursing, nuclear and aeronautical engineering, addiction counseling, and special education, among other fields. Falsely identifying herself as a Liberian official, the principal owner of St. Regis wrote to the University of Illinois in 2003 threatening legal action over information I had posted to a university web page. The resulting brawl led to a multi-agency federal criminal investigation: prosecutors indicted the owners and staff of St. Regis for mail fraud, wire fraud, money laundering, and bribery of foreign officials in late 2005. All eight defendants pled guilty; five began serving prison terms in late 2008. This is a serious issue. The investigation revealed an alarming mix of consumer protection, public safety, and national security issues raised by the activities of the Saint Regis group. In addition, the delay in Liberia's recovery from two decades of civil war, due to the corrupting influences of the St. Regis organization, convolves with Liberia's infant mortality rate in a ghastly calculus of death. And we now see a next-generation diploma mill, having learned from St. Regis' mistakes, attacking the higher education systems in the two African nations immediately to the west of Darfur. We are beginning to make progress. New federal legislation intended to begin the long process of obliterating the diploma mill industry is a direct result of the St. Regis case. Several states have also drafted new laws, or otherwise tightened their oversight of degree providers. But it is an international problem of great complexity, and we are slow to respond. I will tell you stories, all of which are true.
Colloquium
Friday, April 24, 2009
4:00 PM
Physics Building, Room 204

## "The Quantum Mechanics of Global Warming"

[Host: Paul Fendley]
ABSTRACT:
Quantum mechanics plays a crucial, albeit often overlooked, role in our understanding of the Earth's climate. In this talk three well known aspects of quantum mechanics are invoked to present a simple physical picture of what may happen as the concentrations of greenhouse gases such as carbon dioxide continue to increase. Historical and paleoclimatic records are interpreted with some basic astronomy, fluid mechanics, and the use of fundamental laws of physics such as the conservation of angular momentum. I conclude by discussing some possible ways that theoretical physics might be able to contribute to a deeper understanding of climate change.
SLIDESHOW:
Colloquium
Friday, April 17, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Non-Abelian anyons: New particles for less than a billion"

Kirill Shtengel , UC Riverside
[Host: Israel Klich]
ABSTRACT:
The notion of quantum topological order has been a subject of much interest recently, in part because it falls outside of the well-established Landau paradigm whereby states of matter are classified according to their broken symmetries. Topologically ordered phases cannot be described by any local order parameter, yet they have many peculiar properties clearly distinguishing them from the conventionally disordered phases. For example, in two dimensions, they may support anyonic excitations - the quasiparticles that are neither bosons nor fermions. Moreover, anyons with *non-Abelian* braiding statistics are expected to occur, particularly in the fractional quantum Hall regime. Interesting in their own right, such systems may also provide a platform for topological quantum computation. Interferometric experiments are likely to play a crucial role in both determining the non-Abelian nature of these states and in their potential applications for quantum computing. I will discuss solid state interferometers designed to detect such non-Abelian quasiparticle statistics. Should these experiments succeed, such interferometers could also become key elements in a topological quantum computer.
Colloquium
Friday, April 10, 2009
4:00 PM
Physics Building, Room 204

## "High Temperature Superconductivity - After 23 years, where are we at? "

Mike Norman , Argonne National Laboratory
[Host: Despina Louca]
ABSTRACT:
The field of high temperature cuprate superconductivity remains as controversial as ever. Although certain matters have been settled, for instance the symmetry of the order parameter, there is no accepted microscopic framework for describing these materials. This might seem surprising given their relatively simple electronic structure, but the issues involved touch some of the most fundamental ones facing physics - in particular the problem of how to properly treat strong correlations between electrons. In this talk, I will discuss the progress that has been made, but also the many issues that will have to be resolved before we can say that we have "solved" the cuprate problem.
SLIDESHOW:
Colloquium
Friday, April 3, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Quantum Manipulation of Neutral Atoms Without Forces"

Thad Walker , University of Wisconsin
[Host: Tom Gallagher]
ABSTRACT:
Interactions between pairs of Rydberg atoms can be so strong that the energy level structure of one atom is dramatically altered by the presence of a second atom 10 microns away. This "Rydberg blockade" is predicted to allow conditional quantum manipulation of individual atoms based on the quantum state of a distant neighboring atom. When successful, the resulting entanglement process occurs without the atoms experiencing any significant interatomic forces. I will describe experiments at the University of Wisconsin that demonstrate blockade-conditioned coherent evolution of a single Rb atom based on the quantum state of a second atom 11 microns away. Extensions of these ideas to deterministic single atom and single photon sources with atomic ensembles will be presented.
SLIDESHOW:
Colloquium
Friday, March 27, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Beyond E=mc^2: Using Rare Particle Decays to Probe the Energy Frontier"

Craig Dukes , University of Virginia
[Host: Jongsoo Yoon]
ABSTRACT:
Although there is great excitement in particle physics these days, with the advent of the Large Hadron Collider upon us and the great discoveries we hope it will bring, for the first time in some seventy years there are no plans for any new accelerators to take us to the next energy regime. So we will need to look for tiny indirect signs such as rare particle decays in order to find out what may be lurking beyond what we can directly produce in collisions at particle accelerators. There is a long history of such searches for new physics, a history that predates particle physics itself. I will show how such searches will probe mass scales unobtainable by any conceivable particle accelerator and describe the types of accelerators and experiments that are being planned, in particular a very high-sensitivity search for lepton flavor violation in muon decays.
SLIDESHOW:
Colloquium
Friday, March 20, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Graphene-Based Electronics"

Nathan Guisinger , Argonne
[Host: Keith Williams]
Colloquium
Thursday, March 12, 2009
2:00 PM
MEC, Room 205

 Available Colloquium Friday, February 27, 2009 4:00 PM Physics Building, Room 204  Add to your calendar

## "FRIB: A New Accelerator Facility for the Production of Radioactive Beams"

Richard York , MSU
[Host: Blaine Norum]
ABSTRACT:
The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the âconstruction of a Facility for Rare Isotope Beams (FRIB) a world-leading facility for the study of nuclear structure, reactions, and astrophysics. Experiments with the new isotopes produced at FRIB will lead to a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, provide an understanding of matter in the crust of neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society.â A heavy-ion driver driver linear accelerator (linac) will be used to provide stable beams of >200 MeV/u at beam powers up to 400 kW that will be used to produce rare isotopes. Experiments can be done with rare isotope beams at velocities similar to the linac beam, at near zero velocities after stopping in a gas cell, or at intermediate (0.3 to 10 MeV/u) velocities through reacceleration. An overview of the science and the design proposed for implementation on the campus of Michigan State University leveraging the existing infrastructure will be presented.
Colloquium
Friday, February 20, 2009
4:00 PM
Physics Building, Room 204

## "Electrons and Mirror Symmetry"

Kent Paschke , University of Virginia
[Host: Dinko Pocanic]
SLIDESHOW:
Colloquium
Friday, February 13, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Studying strong and electroweak interactions using electron scattering at Jefferson Lab"

Xiaochao Zheng , University of Virginia
[Host: Dinko Pocanic]
ABSTRACT:
I will present two research topics of Jefferson Lab: The first topic is focused on a planned precision measurement of the parity violating asymmetry in e-2H deep inelastic scattering (PVDIS). This asymmetry is sensitive to the electroweak neutral coupling $C_{2q}$ of the Standard Model. The experiment (E08-011) has been approved to run from November to December 2009. I will present the progress in the preparation of E08-011, in particular the development of a new fast-counting DAQ system. The second topic is on the extraction of double and single-target spin asymmetries of pion electro-production using JLab Hall B(CLAS)/EG4 data. We expect to extract these asymmetries in the very low $Q^2$ region Q^2<0.1 (GeV/c)^2. These data will provide important inputs to global analyses of the nucleon resonance structure. Preliminary results using a 3 GeV beam and a NH$_3$ target will be presented.
SLIDESHOW:
Colloquium
Friday, February 6, 2009
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 Available [Host: Jongsoo Yoon] Colloquium Friday, January 30, 2009 4:00 PM Physics Building, Room 204  Add to your calendar

## "The Quantum Spin Hall Effect and Topological Band Theory"

Charlie Kane , U. Penn
[Host: Israel Klich]
ABSTRACT:
A topological insulator is a material with a bulk excitation gap generated by the spin orbit interaction, which is topologically distinct from an ordinary insulator. This distinction - characterized by a topological invariant - necessitates the existence of gapless metallic states on the sample boundary, which have important implications for electronic transport. In two dimensions, the topological insulator is a quantum spin Hall insulator, which is a close cousin of the integer quantum Hall state. In this talk we will outline our theoretical discovery of this phase and describe two recent experiments in which the signatures of this effect have been observed. (1) Transport experiments on HgTe/HgCdTe quantum wells have demonstrated the existence of the edge states predicted for the quantum spin Hall insulator. (2) Photoemission experiments on the semiconducting alloy Bi_{1-x} Sb_x have observed the signature of the gapless surface states predicted for a three dimensional topological insulator. We will close by arguing that the proximity effect between an ordinary superconductor and a 3D topological insulator leads to a novel two dimensional interface state which may provide a new venue for realizing proposals for topological quantum computation.
Colloquium
Friday, January 23, 2009
4:00 PM
Physics Building, Room 204

 RESERVED Colloquium Friday, January 16, 2009 4:00 PM Physics Building, Room 204  Add to your calendar

## "The study of neutron quantum states in the Earth's gravitational field"

Stefan Baessler , University of Virginia
[Host: Dinko Pocanic]
ABSTRACT:
I will discuss the discovery and characterization of gravitational bound neutron states. In the previous experiments, the lowest neutron quantum states in the gravitational potential were distinguished and characterized by a measurement of their spatial extent. The future detection of resonant transitions between these neutron quantum states with the help of the GRANIT spectrometer (under construction) promises to give further and more precise information. Here, transitions between different quantum states induced by RF pulses shall be observed. These measurements are not only demonstrations of standard quantum mechanics. I will discuss applications of these measurements in the search for spin-dependent short-range interactions.
SLIDESHOW:
Colloquium
Friday, December 5, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Cavity optomechanics"

Pierre Meystre , University of Arizona
[Host: Tom Gallagher]
ABSTRACT:
Recent experimental advances in laser cooling have brought macroscopic oscillators closer than ever before to operating in the quantum regime. Fundamental interest in this frontier lies in the fact that quantum mechanics has never been tested at such a macroscopic scale, particularly with respect to counter-intuitive effects such as superposition and entanglement. From a more practical point of view, mechanical oscillators operating in the quantum offer considerable promise as sensors whose precision is fundamentally restricted by quantum mechanics. The talk will present a broad review of the basic principles of the laser cooling of opto-mechanical cantilevers, and then turn to a discussion of some possible applications in the coherent control of atomic and molecular systems.
SLIDESHOW:
Colloquium
Friday, November 21, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Novel Physics with Frozen-Spin Polarized Solid Hydrogen"

Andy Sandorfi , JLab
[Host: Blaine Norum]
SLIDESHOW:
Colloquium
Friday, November 14, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Quantum-limited measurements: One physicist's crooked path from quantum optics to quantum information"

Carl Caves , University of New Mexico
[Host: Olivier Pfister]
ABSTRACT:
Quantum information science has changed our view of quantum mechanics. Originally viewed as a nag, whose uncertainty principles restrict what we can do, quantum mechanics mechanics is now seen as a liberator, allowing us to do things, such as secure key distribution and efficient computations, that could not be done in the realistic world of classical physics. Yet there is one area, that of quantum limits on high-precision measurements, where the two faces of quantum mechanics remain locked in battle. Using my own career as a convenient backdrop, I will trace the history of quantum-limited measurements, from the use of nonclassical light to improve the phase sensitivity of an interferometer, to the modern perspective on how quantum entanglement can be used to improve measurement precision, and finally to how to do quantum metrology without entanglement.
SLIDESHOW:
Colloquium
Friday, November 7, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "SCIENTIFIC CHALLENGES IN HYDROGEN STORAGE: BREAKTHROUGHS AT UVa"

Bellave Shivaram , University of Virginia
[Host: Jongsoo Yoon]
ABSTRACT:
I will describe results of recent experiments at UVa which have revealed that hydrogen storage upto 14 wt.% can be achieved. This is a world record for hydrogen uptake. I will also review the significant scientific challenges that remain and discuss possible solutions. Related work in other laboratories will be discussed as well.
SLIDESHOW:
Colloquium
Friday, October 31, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Magnetic field-induced phase transition in a quantum gapped system: is the Bose-Einstein condensation concept useful?"

Seunghun Lee , University of Virginia
[Host: Dinko Pocanic]
Colloquium
Thursday, October 30, 2008
4:00 PM
Physics Building, Room 204

Mark Adams , Vice President, ITT Corporation
[Host: Bascom Deaver]
ABSTRACT:
Mr. Adams discusses a number of poignant experiences as an undergraduate Physics major at UVA and traces how these lessons have been foundational in his approach to building businesses throughout his career. The technical and operational challenges of remaking a failed $7B company with annual losses exceeding$1B are described from the perspective of a closet physicist. Mr. Adams relates his physics inspired approaches â ranging from the futile to the fruitful â to creating an organization that supports over 300,000 subscribers in over 100 countries worldwide. He also discusses the physics behind his second business startup, which has grown to over a hundred professionals with locations in three states.
Colloquium
Friday, October 24, 2008
4:00 PM
Physics Building, Room 204

## "Bending Back the Light: The science of negative refraction"

Costas Soukoulis , Ames Lab
[Host: Michael Fowler]
SLIDESHOW:
Colloquium
Friday, October 17, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 Available [Host: ] Colloquium Friday, October 10, 2008 4:00 PM Physics Building, Room 204  Add to your calendar

## "Detecting Cosmic Messengers with Antarctic Balloon Flights "

Eun-Suk Seo , University of Maryland
[Host: Seunghun Lee]
ABSTRACT:
Cosmic rays bring us information about physical processes that accelerate particles to relativistic energies, the effects of those particles in driving dynamical processes in our Galaxy, and the distribution of matter and fields in interstellar space. These cosmic messengers can far exceed the energies produced by man-made particle accelerators on Earth. Balloon-borne instruments configured with particle detectors are flown in Antarctica to study cosmic-ray origin, acceleration and propagation. They are also used to explore a possible supernova acceleration limit and to search for exotic sources such as dark matter and antimatter. Our on-going efforts with balloon-borne experiments will be presented and challenges of extending precision measurements to highest energy practical will be discussed.
Colloquium
Friday, October 3, 2008
4:00 PM
Physics Building, Room 204

## "The Ancient Science of Violinmaking"

Oded Kishony , Charlottesville, Violinmaker
[Host: Keith Williams]
SLIDESHOW:
Colloquium
Friday, September 26, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, September 19, 2008 4:00 PM Physics Building, Room 204  Add to your calendar

## "Neutrinos, and the dark side of the light fermions"

Alexander Kusenko , UCLA
[Host: PQ Hung]
ABSTRACT:
The past decade has been marked by some remarkable discoveries in the neutrino physics: the particles once believed to be massless have turned out to be massive and have shown evidence of lepton family number violation, as well as other interesting phenomena. While this is exciting, the future may hold even more dramatic discoveries, the hints for which begin to appear in astrophysics and cosmology. The observed neutrino masses imply the existence of some yet undiscovered "right-handed" states, which can be very massive and unreachable, but which can also be light enough to constitute the cosmological dark matter and to account for a number of astrophysical phenomena, from supernova asymmetries and the pulsar kicks to the peculiarities in the reionization and formation of the first stars. I will review the recent progress in neutrino physics, as well as the clues that may lead to future discoveries.
SLIDESHOW:
Colloquium
Friday, September 12, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Photon Wave Mechanics and Spin-Orbit Interaction in Single Photons"

Michael Raymer , University of Oregon
[Host: Olivier Pfister]
ABSTRACT:
We often use the term âphotonâ in reference to individual quantum objects, or particles of light, rather than as excitations of the electromagnetic field. Yet, quantum mechanics textbooks contain no satisfactory wave equation for the photon wave function. I review the analog of the Dirac equation for a photon, which completely describes the evolution of the photonâs quantum wave function in coordinate space. Single photons carry orbital angular momentum as well as spin angular momentum. When a single photon travels in a multimode optical fiber, its spin and orbital angular momenta interact, modifying the shape of the photon wave function as it travels. Close analogy of this behavior can be found with that of an electron in a cylindrical potential, in spite of the fact that a photon has no magnetic moment. We are carrying out related experiments to illustrate the usefulness of the photon wave function concept.
SLIDESHOW:
Colloquium
Friday, September 5, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

 Available Colloquium Friday, August 29, 2008 4:00 PM Physics Building, Room 204  Add to your calendar

## "Interaction between a molecular magnet monolayer and a metallic surface"

Kyungwha Park , Virginia Tech
[Host: Keith Williams]
ABSTRACT:
Over the past decade, molecular magnets or single-molecule magnets have drawn considerable attention due to observed magnetic quantum tunneling and interference and a possibility of using them for information storage or devices. There have been so far significant efforts to build and characterize thin films or monolayers of single-molecule magnets on surfaces or single-molecule magnets bridged between electrodes. However, there is need to understand changes of the properties of single-molecule magnets in those environments using atomic-scale simulations. In this regard, we simulate, within density-functional theory, a nanostructure in which prototype Mn12 molecules are adsorbed via a thiol group onto a gold surface. Based on a supercell calculation, we investigate how much charge and spin are transferred between a Mn12 molecule and the metal surface. In addition, we compare the electronic structure and magnetic properties of the nanostructure with those of an isolated Mn12 molecule in the absence and presence of spin-orbit interaction.
SLIDESHOW:
Colloquium
Friday, April 25, 2008
4:00 PM
Physics Building, Room 204

Slideshow (PDF)

## "Is the search for the origin of the highest energy cosmic rays over?"

Alan Watson , Leeds University, England
ABSTRACT:

This question can now be asked because of two results obtained using data recorded at the Pierre Auger Observatory. It has been established, at the 6-sigma level, that the flux of the highest energy cosmic rays is suppressed at energies beyond 5 x 10 19 eV and that above this energy an anisotropy in the arrival directions of the particles is apparent. The arrival directions appear to be associated with sources within the GZK horizon (z ~ 0.018 or 75 Mpc). From these observations it seems probable that we have observed the long-sought Greisen-Zatsepin-Kuzmin effect, demonstrating that ultra-high energy cosmic rays are of extragalactic origin. It is also probable that these particles are protons, thus offering the possibility of insights into features of particle physics at centre-of-mass energies 30 times greater than will be reached at the LHC. Preliminary conclusions from studies of detailed features of extensive air showers suggest that extrapolations from Tevatron energies may not be what have been anticipated hitherto. Much further work remains to be done.

SLIDESHOW:
Colloquium
Friday, April 18, 2008
4:00 PM
Physics Building, Room 203

Joint Astronomy-Physics-NRAO Colloquium

Slideshow (PDF)

## "The Birth of Cosmic Ray Astronomy on the Argentine Pampas"

Alan Watson , University of Leeds, United Kingdom
[Host: Physics Department]
Colloquium
Thursday, April 17, 2008
7:30 PM
Physics Building, Room Chemistry Building, Room 402

Hoxton Lecture

## "Dark Energy and Cosmic Sound"

Daniel Eisenstein , University of Arizona
[Host: Dinko Pocanic]
ABSTRACT:
I present galaxy clustering results from the Sloan Digital Sky Survey that reveal the signature of acoustic oscillations of the photon-baryon fluid in the first million years of the Universe. The scale of this feature can be computed and hence the detection in the galaxy clustering serves as a standard ruler, giving a geometric distance to a redshift of 0.35. I will discuss the implications of this measurement for the composition of the universe, including dark energy and spatial curvature. I will close with a more general discussion of SDSS-III, a new collaborative project that will feature a large redshift survey aimed at refining the acoustic oscillation distance scale to 1% as well as surveys for extrasolar planets and the structure of the Milky Way.
Colloquium
Tuesday, April 15, 2008
4:00 PM
Physics Building, Room 204

Special Colloquium

## "Nucleon Form Factors...50 Years Later"

John Arrington , Argonne National Lab
[Host: Nilanga Liyanage]
ABSTRACT:
The structure of the proton and neutron can be expressed in terms of the electric and magnetic form factors which can be measured from elastic electron-proton scattering. Fifty years ago, the first electron scattering measurements of the proton form factors started the process of mapping out the distribution of charge and magnetization of the proton. Four decades of measurements gave us a simple picture of the nucleon, but our understanding was severely limited by the experimental techniques and theoretical understanding. The last ten years as provided several new experimental and theoretical techniques, giving us a much clearer picture of nucleon structure, and providing a few surprises along the way.
Colloquium
Friday, April 11, 2008
4:00 PM
Physics Building, Room 204

## "Nanoscale Assembly with DNA"

Ned Seeman , NYU
[Host: Keith Williams]
Colloquium
Monday, April 7, 2008
4:00 PM
Wilsdorf Hall, Room Atrium

Special Colloquium

 Available Colloquium Friday, April 4, 2008 4:00 PM Physics Building, Room 204  Add to your calendar

## "Probing Nucleons Inside Nucleus"

Seonho Choi , Seoul National University
[Host: Nilanga Liyanage]
ABSTRACT:
The interior world of the nucleus is still a mystery in nuclear physics. While it is well known that the nucleus is made of nucleons, their properties inside the nucleus are still a big puzzle. There has been a series of experiments to probe the nucleons inside the nucleus. However, the results are still controversial. One main remaining question is regarding the Coulomb Sum Rule (CSR). The colloquium will cover the basic concept of probing microscopic world with high energy electron beams, the key issues of the CSR problem and the recent, new experiment at Jefferson Lab to study the CSR problem.
Colloquium
Friday, March 28, 2008
4:00 PM
Physics Building, Room 204

 Available Colloquium Friday, March 21, 2008 4:00 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, March 14, 2008 4:00 PM Physics Building, Room 204  Add to your calendar
 Available Colloquium Friday, February 29, 2008 4:00 PM Physics Building, Room 204  Add to your calendar

## "Fermilab's race for the Higgs boson"

Benjamin Kilminster , Ohio State University
ABSTRACT:
One of the most important mysteries in our understanding of the universe is how elementary particles acquire mass. Our best explanation for this requires the existence of a particle called the Higgs boson, which has not yet been directly observed. Particle physicists at Fermilab, near Chicago, are currently capable of producing and detecting Higgs bosons from collisions of matter and antimatter at very high energies. I will explain what exactly these physicists are looking for, and present the experimental challenges involved in a few particular methods for differentiating Higgs bosons from other background processes. Finally, I will discuss future prospects for Higgs boson discovery at Fermilab, as well as the discovery potential of future experiments.
Colloquium
Friday, February 22, 2008
4:00 PM
Physics Building, Room 204

## "W Bosons and b Quarks at the Tevatron: Understanding the Haystack to Help Find the Needle"

Christopher Neu , University of Pennsylvania
ABSTRACT:
Particle physics is at the threshold of an exciting new era. A crucial experimental pursuit is the search for and observation of the Higgs boson, a prominent missing piece in the widely successful standard model of the fundamental world. Searches at the Tevatron proton-antiproton collider in Illinois are closing in on the Higgs, while experiments at the new Large Hadron Collider in Switzerland are scheduled to begin operations later this year. One of the main signatures for the Higgs contains a W boson and one or more b quarks. However, this signature is shared by more common electroweak and strong processes that have not been determined precisely by experiment until now. Herein I will present a new measurement by CDF of W boson and b quark production. This measurement will contribute to improvements in the theoretical models, and I will discuss how this result can be used to sharpen searches for the Higgs and for physics beyond the standard model at both the Tevatron and the Large Hadron Collider.
SLIDESHOW:
Colloquium
Wednesday, February 20, 2008
3:30 PM
Physics Building, Room 204

Slideshow (PDF)