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 Physics at Virginia

"TBA"


Gray Rybka , University of Washington
[Host: David Nichols & Bradley Johnson]
ABSTRACT:

TBA

Colloquium
Friday, April 26, 2024
3:30 PM
, Room TBA
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"TBA"


Stefan Baessler , UVA-Department of Physics
[Host: Dinko Pocanic]
ABSTRACT:

TBA

Colloquium
Friday, March 15, 2024
3:30 PM
, Room TBA
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"Sigma Pi Sigma Research Symposium Presentations"


Olivia Mostow/Sam Crowe/Alex Rosenthal , University of Virginia
[Host: Jency Sundararajan]
ABSTRACT:

Olivia Mostow:  The Core-Cusp Problem in Low-Mass Galaxies: Is One Burst Enough? (15 minutes)

We present a novel method for assessing the ability of a single burst of star formation to transform dark matter cusps into cores in low-mass galaxies. Following the approach of Rose et al. 2022, we manually add a contribution to the potential that accounts for a centrally concentrated baryon component within an otherwise dark matter only simulation. This approach allows us to maintain control over how and when these bursts occur. We demonstrate that this method can reproduce the established result of core formation for systems that undergo multiple episodes of bursty outflows. In contrast, we find that equivalent models that undergo only a single (or small number) of burst episodes do not form cores with the same efficacy. This is important because many low-mass galaxies in the local universe are observed to have tightly constrained star formation histories that are best described by a single, early burst of star formation. Using a suite of cosmological, zoom-in simulations, we identify the regimes in which single bursts can and cannot form a cored density profile, and therefore, can or cannot resolve the core-cusp problem.

Sam Crowe:  Unveiling Massive Star Formation: Near-Infrared Observations of Protostellar Jets (15 Minutes)

Massive stars are significant throughout the universe, as they impact their surroundings from the early stages of their formation until they die in the form of supernova. Observations in the near-infrared (NIR) of the bright and large-scale (~parsec) jets that young stars ubiquitously produce during their formation process can place important constraints on the phenomenon of massive star formation. Here, I present a detailed NIR view of two massive star-forming complexes at opposite ends of the sky, AFGL 5180 and Sagittarius C, utilizing extremely high-resolution imaging from the Large Binocular Telescope, Hubble Space Telescope, and James Webb Space Telescope. In AFGL 5180, the data reveal several multidirectional outflows indicative of highly clustered star formation, confirmed by the detection of over a dozen compact sub-millimeter sources using data from the Atacama Large Millimeter/Submillimeter Array (ALMA). By sampling the number density of young stellar objects in the vicinity of the central massive (~12 Msun) protostar, and comparing with recent numerical simulations, we present a novel method for directly distinguishing between theories of massive star formation in situ. Conversely, in Sagittarius C, located in the turbulent and chaotic center of our Milky Way, we find relatively ordered and isolated massive star formation, evidenced by collimated and undisturbed NIR jets. We report the discovery of a new star-forming region ~1 arcminute to the west of Sagittarius C, hosting two prominent bow shocks visible in the NIR imaging, and characterize the most luminous protostar in each neighboring complex via ancillary ALMA data and Spectral Energy Distribution fitting, shedding light on how the process of massive star formation is unfolding in this extreme region.

Alex Rosenthal:  Mass-Loss Rates for Massive Stars from Stellar Bowshocks (15 Minutes)

Massive stars lose a significant portion of their mass through stellar winds over the course of their lifetime, and understanding the rate of mass-loss is critical for understanding stellar evolution and compact object genesis. Traditional methods of determining mass-loss rates rely on UV observations and parameterizing a “clumping” factor, which varies significantly and results in a two-order-of-magnitude difference between prediction and observation for stars with weak winds. We intend to address this “weak-wind problem” using a novel method to measure mass-loss rates of massive stars powering stellar bowshocks using optical spectroscopy of the central stars, far infrared measurements of the bowshock nebulae, and space velocities calculated from GAIA DR3 proper motions. This method utilizes the geometry of the bowshock and the principle of balancing the momentum flux between stellar winds and ambient interstellar material to make a mass-loss rate determination. We observed late-O and early-B type stars with bowshocks with the Apache Point Observatory 3.5m telescope with the KOSMOS long-slit spectrograph and the Wyoming Infrared Observatory’s 2.3m telescope with an optical spectrograph. We used the emcee package in Python and interpolated between models from the PoWR OB-I grid to fit their spectra to find temperatures and surface gravities. We found that our sample spanned a range of stellar parameters, with temperatures varying from 16,000-38,000 K and the log of surface gravity ranging from 2.8-4.1 dex. Using these parameters and photometric data, we calculated predicted mass-loss rates. This work is supported by the National Science Foundation under REU grant AST 1852289

Colloquium
Friday, February 9, 2024
3:30 PM
Clark Hall, Room 107
Note special room.

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

 


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"The Electron-Ion Collider : The Next QCD Frontier"


Renee Fatemi , University of Kentucky
[Host: Simonetta Liuti]
ABSTRACT:

The Electron-Ion Collider (EIC) is a pioneering new particle accelerator that will be built on the current site of the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. It will provide high energy collisions of polarized electrons with polarized protons and ions, allowing for experiments that probe the nature of strong interactions to unprecedented precision. The EIC Project has grown and evolved rapidly since the official launch by the U.S. Department of Energy in 2020. This talk will discuss the primary physics themes driving the EIC effort, the recent milestones achieved by the project and the efforts to establish two complementary detectors at adjacent interaction regions. 

Colloquium
Friday, February 2, 2024
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"Two tales about time in living (and not-so-living) transport networks"


Eleni Katifori , University of Pennsylvania
[Host: Marija Vucelja]
ABSTRACT:

We utilize transport systems daily to commute, e.g. via road networks, or bring energy to our houses through the power grid. Our body needs transport networks, such as the lymphatic, arterial or venous system, to distribute nutrients and remove waste. If the transported quantity is information, for example carried by an electrical signal, then even the internet and the brain can be thought of as members of this broad class of webs. Despite our daily exposure to transport networks, their function and physics can still surprise us. This is exemplified by the Braess paradox, where the addition of an extra road in a network worsens rather than improves traffic contrary to a naïve prediction.

In this talk we will explore two cases that highlight the importance of time in load transmission in transport networks. In the first problem, we will discuss how short timescale dynamics in the flow alters the topology of the network in longer timescales, and shapes its morphology. We will first present the system of phenomenological adaptation equations that govern the structural evolution of vascular networks. We will then demonstrate how implicit of explicit dynamics in the boundary conditions (the power supply, or heart) can drastically alter the network topology, and discuss the implications for the development and function of human circulation. Moving to a larger system, will provide evidence that the similar dynamical developmental rules to the ones that are thought to control vascular remodeling in humans also shape tidal delta geomorphology. 

In the second problem, we consider stochastic transport in geometrically embedded graphs. Intuition suggests that providing a shortcut between a pair of nodes improves the time it takes to randomly explore the entire graph. Counterintuitively, we find a Braess' paradox analog. For regular diffusion, shortcuts can worsen the overall search efficiency of the network, although they bridge topologically distant nodes. We propose an optimization scheme under which each edge adapts its conductivity to minimize the graph's search time. The optimization reveals a relationship between the structure and diffusion exponent and a crossover from dense to sparse graphs as the exponent increases.

Colloquium
Friday, January 19, 2024
3:30 PM
Clark Hall, Room 107
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"Chasing the Ghost Particle: Neutrino Astrophysics with IceCube"


Brian Clark , University of Maryland
[Host: Craig Group]
ABSTRACT:

High energy (> TeV) neutrinos are unique messengers to the distant, high-energy universe. As chargeless and weakly interacting particles, neutrinos arrive from cosmic distances, giving us insights to the nature of astrophysical accelerators like black holes and gamma ray bursts. In this talk, I will discuss the ongoing work of the IceCube Neutrino Observatory to detect and study extraterrestrial neutrinos. I will review how the IceCube detector, which is a cubic kilometer instrument buried deep at the South Pole, detects high energy neutrinos. I will then discuss the latest physics results of the detector, including efforts to measure and characterize the high energy neutrino flux and to find neutrino sources.

Colloquium
Friday, December 1, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"Toward Fusion Energy Production Using Spin-Polarized Nuclear Fuel"


Wilson G Miller , UVA MD-RADL Rad Research
[Host: Xiaochao Zheng]
ABSTRACT:

Thermonuclear fusion of deuterium (D) and tritium (T) in a magnetically confined plasma is the most widely pursued path to large-scale fusion energy production. However, achieving a burning plasma capable of self-sustained energy production remains an elusive goal. The use of spin-polarized fuel could provide a significant boost, as the reaction rate for D + T → α + n increases by 50% if the spins of the reacting nuclei are oriented parallel to each other, and both along the local magnetic field.  A multicenter collaboration including the University of Virginia and Jefferson Lab is working toward the first direct test of spin-polarized fusion in the DIII-D tokamak in San Diego, using the isospin-mirror reaction D + 3He → α + p. This talk will give an overview of our DOE-funded fusion research program, and further describe the cross-grounds work being performed at the UVA Medical School toward optimizing polarized 3He fuel preparation using Magnetic Resonance Imaging.

Colloquium
Friday, November 17, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"Photons in the spotlight "


Daniel Tapia Takaki , University of Kansas
[Host: Simonetta Liutu]
ABSTRACT:

The study of ultraperipheral nuclear collisions (UPCs) is breaking new grounds in fundamental physics. Although experiments at BNL RHIC and at the CERN LHC are not designed to exploit photon-induced interactions there is a plethora of recent results on UPCs in a wide variety of subjects:  imaging the nucleus, studying fundamental electromagnetic and electroweak processes, probing the Quark-Gluon Plasma,  and searches for physics beyond the Standard Model. In this talk, we will discuss a selection of recent UPC studies, as well as new directions in light of new theoretical and phenomenological studies, including novel applications of quantum mechanics.

Colloquium
Friday, November 10, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"The Chemistry of Quantum Materials"


Leslie Schoop , Princeton University
[Host: Dima Pesin]
ABSTRACT:

Quantum materials are hoped to change technology in various aspects. However, most of the desired applications are hindered by the lack of suitable materials. In my group we are using concepts from chemistry to understand, predict and synthesize new quantum materials. In this talk, I will show how simple concepts, such as measuring bond distances, allow us to make predictions about electronic structures of materials, which we can then use to find new topological materials. We then can combine this with structural building blocks containing magnetic elements to design materials with non-colinear or even non-coplanar magnetism. I will give a general overview how powerful chemical concepts are in materials discovery and highlight a flute of materials that were discovered in this light.

Colloquium
Friday, November 3, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"Patience is a virtue: The 15-year NANOGrav Gravitational Wave Results"


Scott Ransom , NRAO
[Host: Department of Physics]
ABSTRACT:

Earlier this summer, the pulsar timing array community announced strong evidence for the presence of a stochastic background of nanoHertz frequency gravitational waves. This has been the primary goal of the community for the past two decades, and it took thousands of hours of telescope time, over 500,000 pulse arrival times from ~70 millisecond pulsars, and a highly sophisticated and very computationally demanding analysis effort to accomplish. While we can't yet say for certain what is causing the gravitational waves, our best guess is a population of slowly merging super-massive black hole binaries throughout the universe. But it is possible that the signal also heralds new physics. So what does it all mean and what are we expecting next? And what other cool things can we do with all of this high-precision pulsar data?

Colloquium
Friday, October 27, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"Scaling in Many Body Quantum Spin Systems"


Bellave Shivaram , UVA
[Host: David Nichols]
ABSTRACT:

In the absence of a detailed first principles based understanding of condensed matter phenomena a scaling approach is many times a good starting point. Although it is also true that scaling in physical properties and laws can also be a consequence or flow out of more fundamental theories.  In this talk I will examine two rather different physical systems, one metallic and the other primarily insulating, where scaling ideas have helped us to understand our measurements.  In the heavy fermion (metallic) systems I will review our work on scaling properties observed in their magnetic, ultrasonic and thermal response.  In a quantum spin liquid system (insulating) I will describe recent work where scaling ideas have led to advances in understanding of a candidate Dirac Quantum Spin liquid.

Colloquium
Friday, October 20, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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ABSTRACT:

The gyromagnetic ratio g for an elementary point-particle differs from the Dirac value of g = 2 by the “magnetic anomaly” a = (g − 2)/2 ≈ 10−3, due to couplings to virtual particles in the vacuum. Muon, through its greater mass, probes significantly deeper into the high-mass excitations of the vacuum than does the better studied electron. Hence, efforts to measure the muon magnetic anomaly aµ have persisted for decades, culminating in Fermilab E989, the Muon g−2 experiment. In July 2023, the E989 collaboration concluded data taking in Run-6, its last run cycle, and a few weeks later unblinded and published results of Run-2 and -3 data analysis, adding to the Run-1 results of 2021. The Run-2/3 results bring about a two-fold improvement in the precision of the world average of aµ. In parallel, recent theoretical and experimental developments regarding the hadronic vacuum polarization (HVP) have led to a reexamination of the context for the interpretation of the experimental value of aµ. This talk will examine the experimental method, uncertainties, and results of E989. We will place the new aµ result in the context of a changing HVP landscape, and discuss the future prospects for the field.

Colloquium
Friday, October 13, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"Direct Detection of sub-GeV Dark Matter: A New Frontier"


Rouven Essig , Stony Brook University
[Host: Craig Group]
ABSTRACT:

Dark matter makes up 85% of the matter in our Universe, but we have yet to learn its identity.  While most experimental searches focus on Weakly Interacting Massive Particles (WIMPs) with masses above the proton (about 1 GeV/c^2), many natural dark-matter candidates have masses below the proton and are invisible in traditional WIMP searches.  In this talk, I will discuss the search for dark matter with masses between about 500 keV/c^2 to 1 GeV/c^2 (“sub-GeV dark matter”), which has seen tremendous progress in the last few years.  I will describe several direct-detection strategies, and discuss how to search for dark matter interactions with electrons and nuclei in various target materials, such as noble liquids and semiconductors.  I will in particular highlight SENSEI, a funded experiment that will uses new ultra-low-threshold silicon CCD detectors (“Skipper CCDs”) capable of detecting even single electrons.  I will describe the latest results from SENSEI, and how we expect to probe orders of magnitude of novel dark matter parameter space in the next few years.  

VIDEO:
Colloquium
Friday, September 15, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"A NICER view of neutron stars"


M. Coleman Miller , University of Maryland
[Host: David Nichols]
ABSTRACT:

Precise and reliable measurements of neutron star radii are essential to our understanding of cold, catalyzed matter beyond nuclear saturation density.  Recently, NASA's Neutron Star Interior Composition Explorer (NICER) satellite has provided high-quality data sets that have yielded measurements of the mass (M=1.44+-0.15 Msun) and radius (R=13+1.2-1.0 km) of the 206 Hz pulsar PSR J0030+0451, and of the radius (R=13.7+2.6-1.5 km) of the M=2.08+-0.07 Msun, 346 Hz pulsar PSR J0740+6620.  I will discuss our group's work on these pulsars and will in particular discuss the assumptions that have gone into our analyses, to help in the assessment of our results.  I will also discuss the implications of our results, combined with other observations including of gravitational waves, for the properties of the dense matter in the cores of neutron stars.

VIDEO:
Colloquium
Friday, September 8, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"Anomalous thermal relaxations of physical systems"


Marija Vucelja , UVA-Department of Physics
[Host: Despina Louca]
ABSTRACT:

Rapid cooling or heating of a physical system can lead to unusual thermal relaxation phenomena. A prime example of anomalous thermal relaxation is the Mpemba effect. The phenomenon occurs when a system prepared at a hot temperature overtakes an identical system prepared at a warm temperature and equilibrates faster to the cold environment. A similar effect exists in heating. Comparing two identical physical systems in their equilibration, we would expect that the system with a smaller mismatch between its and the environment’s temperature will thermalize faster – yet it is not always the case. I will present theoretical results on the Mpemba effect in over-damped Langevin dynamics and Markov jump processes. I will link the Mpemba effect’s occurrence with the physical systems’ properties and dynamics. In particular, I will derive the necessary conditions for the Mpemba effect in the small diffusion limit of one-dimensional over-damped Langevin dynamics on a double-well potential. Our results show the strong Mpemba effect occurs when the probability of being in a well at initial and bath temperature match, which agrees with experiments. I also derive the conditions for the weak Mpemba effect and express the conditions for both effects in terms of mean first passage time. Next, I will provide analytical results and insights on when the Mpemba effect happens in Markov jump processes as a function of the dynamics. Markov jump processes that obey detailed balance (microscopic reversibility) relax to equilibrium. However, the detailed balance only determines the ratio of the backward and forward rates, not their magnitudes. The magnitudes specify the dynamics. I will introduce a control parameter to vary the dynamics and show when we see the effect as a function of the dynamics. Lastly, I will explore the connections between the Mpemba effect and optimal transport. This material is based upon work supported by the National Science Foundation under Grant No. DMR-1944539.

VIDEO:
Colloquium
Friday, September 1, 2023
3:30 PM
Clark Hall, Room 107
Note special room.

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


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"Quantum many-body physics with ultracold atoms "


Peter Schauss , Univerisy of Virginia - Physics
[Host: Despina Louca]
ABSTRACT:

Single-particle control and detection of strongly correlated quantum many-particle systems has enabled a wide variety of applications including quantum simulation of condensed matter systems and quantum computing demonstrations. Exact numerical simulations on classical computers are intractable for most quantum many-body systems beyond a few particles. Quantum simulators can answer questions by implementing the Hamiltonian of interest, while digital quantum computers realize universal quantum computing using a set of gates.

 

In the first part of the talk, I will give an introduction into the field of quantum simulation using ultracold atoms with focus on quantum gas microscopy techniques which allow us to probe many-body systems at the single-particle level. Over the past years, we developed a platform to study geometrically frustrated Hubbard systems and reveal their quantum correlations. We prepared fermionic atomic Mott insulators on a triangular lattice, detected them with single-site resolution and measured spin-spin correlations. Currently we are working on upgrades to the experiment which enable the study of kinetic magnetism and exotic quantum phases.

 

The second part of the talk will cover the progress of our new experiment with ytterbium atoms in optical tweezers. I will discuss the advantages and disadvantages of the tweezer platform and present our plans to realize large entangled states.

 

We acknowledge funding by NSF (CAREER award PHY-2047275), ONR (DURIP award N00014-22-1-2681), AFOSR (award FA9550-23-1-0166), the Thomas F. and Kate Miller Jeffress Memorial Trust and the Jefferson Trust.

VIDEO:
Colloquium
Friday, August 25, 2023
3:30 PM
Ridley Hall, Room G004
Note special room.

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


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"Agnostic black hole spectroscopy"


Emanuele Berti , Johns Hopkins University
[Host: David Nichols]
ABSTRACT:

According to general relativity, the remnant of a binary black hole merger should be a perturbed Kerr black hole. Perturbed Kerr black holes emit "ringdown" radiation which is well described by a superposition of quasinormal modes, with frequencies and damping times that depend only on the mass and spin of the remnant. The observation of gravitational radiation emitted by black hole mergers might finally provide direct evidence of black holes with the same certainty as, say, the 21 cm line identifies interstellar hydrogen. I will review the current status of this "black hole spectroscopy" program. I will focus on two important open issues: (1) Is the waveform well described by linear black hole perturbation theory? (2) What is the current observational status of black hole spectroscopy?

VIDEO:
Colloquium
Friday, April 28, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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


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"Dark Matter in the Universe"


Professor Katherine Freese , University of Texas, Austin
[Host: Prof. PQ Hung]
ABSTRACT:

The nature of the dark matter in the Universe is among the longest and most important outstanding problems in all of modern physics. The ordinary atoms that make up the known universe, from our bodies and the air we breathe to the planets and stars, constitute only 5% of all matter and energy in the cosmos. The remaining 95% is made up of a recipe of 25% dark matter and 70% dark energy, both nonluminous components whose nature remains a mystery.  I’ll begin by discussing the evidence that dark matter is the bulk of the mass in the Universe, and then turn to the hunt to understand its nature.  Leading candidates are fundamental particles including Weakly Interacting Massive Particles (WIMPs), axions, sterile neutrinos, as well as primordial black holes.  I will discuss multiple experimental searches:  at CERN in Geneva; in underground laboratories; with space telescopes; with gravitational wave detectors; and even with DNA.  I’ll tell you about our novel idea of Dark Stars, early stars powered by dark matter heating, and the possibility that the James Webb Space Telescope could find them.  At the end of the talk, I'll turn to dark energy and its effect on the future of the Universe.

VIDEO:
Colloquium
Friday, April 21, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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


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ABSTRACT:

Tensor renormalization group (TRG) is an algorithm introduced by Levin and Nave to implement a Migdal-Kadanoff-like iterative coarse-graining scheme for lattice partition sums. It proved remarkably accurate for the 2D Ising models and stimulated considerable further work to understand and improve the technical aspects of the algorithm leading to qualitative improvements in the method.
In this talk I will review (i) the early block spin transformation idea and its TRG implementation; (ii) analyticity constraints on global phase diagrams, including recent results in anisotropic lattices; (iii) and explain the application of these results to realizing temporally ordered dynamic phases in quantum (discrete time) evolution with measurements.

ref:
https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.4.013018

VIDEO:
Colloquium
Friday, April 14, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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


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"Interfacing Quantum Information and Quantum Sensing "


Charlotte Boettcher , Yale
[Host: Despina Louca]
ABSTRACT:

Quantum information is a rapidly growing field that continues to develop and explore a variety of platforms to realize scalable quantum devices. Progress in qubit technology is driven by continued advancement in materials research, which informs fundamental issues such as the underlying mechanisms limiting qubit coherence times. Further, quantum materials including superconductors, magnets, insulators, and topological materials all offer unique properties that can be implemented into quantum circuits to realize new functionalities. In this way, the fundamental physics of quantum materials is intertwined with the development of next-generation quantum devices.
In this talk, I will discuss several topics at the intersection of quantum information and quantum materials research, which demonstrate this symbiotic relationship between the two fields. This includes how one can use Josephson junctions - a critical element of the Transmon qubit - formed into arrays to serve as both a quantum simulator of interacting many-body systems such as the Hubbard model as well as a novel platform to study quantum phase transitions such as the superconductor-to-insulator transition. Additionally, I will discuss how microwave circuits can be used as a sensitive probe of the order parameter symmetry in low-dimensional unconventional superconductors and mesoscopic heterostructures, as well as for a variety of other quantum sensing applications. Finally, I will discuss future opportunities to leverage the interplay between quantum materials and quantum information to both gain insight into enigmatic phases of matter and design novel qubits and quantum devices. 

VIDEO:
Colloquium
Friday, April 7, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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


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ABSTRACT:

Entanglement is the strangest feature of quantum theory, often dubbed ''spooky action at a distance’’. Quantum entanglement can occur on a macroscopic scale with trillions of electrons, leading to "strange metals" and novel superconductors which can conduct electricity without resistance even at relatively high temperatures. Remarkably, related entanglement structures arise across the horizon of a black hole, and give rise to Hawking’s quantum paradox. This lecture will be designed to introduce these forefront topics in current physics research to a general audience.

VIDEO:
Colloquium
Thursday, April 6, 2023
7:00 PM
Gilmer Hall, Room 301
Note special date.
Note special time.
Note special room.

Hoxton Lecture


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"Flatland quantum simulation and visualization with atomic resolution"


Yulia Maximenko , NIST Gaithersburg
[Host: Despina Louca]
ABSTRACT:

Quantum computing and simulation promise to revolutionize fundamental physics, technology, and quantum chemistry. Simulating quantum systems using analog platforms was first proposed in the 1980s, but recent technological advances have brought this idea to new heights. Trapped atoms and ions, superconducting circuits, and advanced solid-state platforms have achieved an unprecedented level of quantum control and are able to model increasingly complex Hamiltonians. Quantum simulation in 2D solid platforms has proved to be incredibly versatile, while also being compatible with the existing semiconductor technology. In this colloquium, I will showcase the exciting recent developments in the field of 2D quantum simulators, highlighting twisted moiré systems and atomic manipulation. Scanning tunneling microscopy (STM) has proved crucial for the progress of this field. My focus will be on revealing the topological and strongly correlated physics in twisted layered graphene and on the surprising insights gained through the use of STM. Through high-resolution magnetic field scanning tunneling spectroscopy, we have demonstrated the importance of the fine details of quantum geometry in these novel 2D platforms. Specifically, I will report on the discovery of an emergent anomalously large orbital magnetic susceptibility in twisted double bilayer graphene, along with the orbital magnetic moment. I will also discuss the exciting future potential in the field of quantum materials, combining STM, epitaxial growth, and stacked 2D devices.

VIDEO:
Colloquium
Wednesday, April 5, 2023
11:00 AM
Ridley Hall, Room G006
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Note special time.
Note special room.

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


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"Scaling down the laws of thermodynamics"


Christopher Jarzynski , University of Maryland
[Host: Marija Vucelja]
ABSTRACT:

Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems also exhibit “thermodynamic­-like” behavior – for instance, biomolecular motors convert chemical fuel into mechanical work, and single molecules exhibit hysteresis when manipulated using optical tweezers. To what extent can the laws of thermodynamics be scaled down to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will describe some of the challenges and recent progress – both theoretical and experimental – associated with addressing these questions.  Along the way, my talk will touch on non-equilibrium fluctuations, “violations” of the second law, the thermodynamic arrow of time, nanoscale feedback control, strong system-environment coupling, and quantum thermodynamics.

VIDEO:
Colloquium
Friday, March 31, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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


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"Tapping into quantumness of condensed matter with color centers"


Prof. Yaroslav Tserkovnyak , UCLA
[Host: Prof. Israel Klich]
ABSTRACT:

Combining low-dimensional correlated condensed matter systems with judiciously placed and optically accessible quantum impurities is a fruitful enterprise for (1) diverse sensing modalities of fundamental equilibrium and transport properties in a variety of systems, (2) designing and building up quantum-entangled dynamics of the quantum bit ensembles, and (3) using such dynamics to imprint measurable quantum correlations back onto the condensed matter systems and devices. This interplay between macroscopically controlled solid-state heterostructures and intricate highly-correlated quantum dynamics of atomistic quantum degrees of freedom opens up a rich and versatile playground for fusing ideas from quantum optics, quantum transport, and quantum material sensing and engineering. I will summarize our current ideas, focusing on the overarching symmetry and nonequilibrium thermodynamics based reasoning.

 

VIDEO:
Colloquium
Friday, March 24, 2023
3:00 PM
Clark Hall, Room 108
Note special time.
Note special room.

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


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"Phases of Particle Dark Matter"


Josh Ruderman , NYU
[Host: Jan Heisig]
ABSTRACT:

Dark matter is believed to make up most of the matter in our Universe, but its particle origin remains a mystery.  A favorite candidate is the so-called Weakly Interacting Massive Particle (WIMP), but a diverse set of experiments are rapidly closing the available parameter space for WIMPs.  I will show that small changes to the assumptions about how dark matter was produced in the early Universe lead to very different dark matter masses and interaction strengths.  I will chart ``phase diagrams” for the production of dark matter with a thermal or non-thermal origin.  I will explain how different phases of dark matter production map onto different experimental prospects.

Colloquium
Friday, March 3, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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


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"Mapping the Local Bubble's Magnetic Field in 3D"


Theo O'Neill , UVA
[Host: Stefan Baessler]
ABSTRACT:

Our solar system is embedded in the Local Bubble, an expanding, 1,000-light-year-wide cavity in the interstellar medium (ISM).  The Bubble was created ~14 million years ago by a chain of supernova explosions that drove out most of the diffuse dust and gas in the nearby ISM.  Recent work mapping the 3D shape and dynamics of the Local Bubble has revealed that nearly all recent star formation within
200 pc of the Sun was triggered by the Bubble's rapid expansion.  The exact mechanics of this expansion, and the role that magnetic fields in the ISM have played in regulating its evolution, is not yet clear.  By combining detailed models of the Bubble’s geometry (derived from 3D dust
mapping) with Planck dust polarization observations and the assumption that magnetic field vectors are tangent to the Bubble’s surface, we are able to infer the Bubble’s 3D magnetic field orientation.  This map is the first to fully chart magnetic fields over an observed superbubble in 3D.  We analyze the relationship between the Local Bubble’s magnetic field and background starlight polarimetry observations, and discuss how magnetic fields may have affected the dynamics of the Local Bubble and progression of nearby star formation.

Colloquium
Friday, February 24, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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ABSTRACT:

Using muon tomography, the Non-invasive Archaeometry Using Muons (NAUM) Project will image the interiors of ancient Maya temples in Chichén Itzá, Mexico to uncover their unknown internal structures.
Conceptually, muon tomography is the nascent science of collecting muon flux measurements through cross sections of an object to graphically visualize the internal massive structure. NAUM’s volumes of interest lie beneath the multi-stacked Maya temples at Chichén Itzá. The Maya city of Chichén Itzá, on the Yucatan Peninsula in Mexico, was a regional capital housing a great deal of historical and cultural significance for the Maya people. By imaging the Temple of Kukulcán with muon tomography, we can non-invasively explore inside this monumental structure while preserving its history and glean information on how and why the scientifically and mathematically intelligent Maya civilization built these great landmarks. This presentation describes the project's history, process, and progress, including results from a trip to Chichén Itzá, muon flux simulations, prototype detector fabrication and testing at the Fermilab Test Beam, and the prototype's resolution analysis.

Colloquium
Friday, February 24, 2023
4:00 PM
Clark Hall, Room 108
Note special time.
Note special room.

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


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ABSTRACT:

Understanding chirality, the intrinsic handedness of a system, is important for future technologies using quantum magnetic materials.  Of particular interest are magnetic skyrmions which are chiral and topologically protected, meaning that their spin textures can act as barriers from deformation in crystalline grains.  However, most electron microscopy studies use Lorentz TEM or holography to investigate chirality in skyrmions in nearly perfect single crystals because Fresnel effects may cause signals from grain structures to be mistaken as magnetism when the two are comparable in size.  In this work, we probe nanomagnetism of topological magnetic textures in sputtered thin film of B20 FeGe on Si to study the relationship between magnetic and crystal chirality.  Using 4D-STEM, we find that the vorticity and helicity of these magnetic topological phases are coupled to the crystal chirality.  Furthermore, our work shows that signals from magnetism can be disentangled from crystalline effects for sub-micron grains, enabling a new way to investigate topological magnetism in the presence of small polycrystalline grains. This methodology is important for spintronics and low-power magnetic memory technologies that rely on scalable techniques for large scale manufacturing of real devices. 

Colloquium
Friday, February 10, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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


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"Machine learning concepts for inverse materials design"


Andrea Liu , University of Pennsylvania
[Host: Marija Vucelja]
ABSTRACT:

In order for artificial neural networks to learn a task, one must solve an inverse design problem. What are all the node weights for the network that will give the desired output? The method by which this problem is solved by computer scientists can be harnessed to solve inverse design problems in soft matter. I will discuss how we have used such approaches to design mechanical and flow networks that can perform functions inspired by biology. I will also show how we can exploit physics to go beyond artificial neural networks by using local rules rather than global gradient descent approaches to learn in a distributed way.

Colloquium
Friday, February 3, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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


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"Unraveling the origin of neutrino masses"


Julian Heeck , UVA-High Energy Physics
[Host: Despina Louca]
ABSTRACT:

Non-zero neutrino masses provide the strongest evidence for physics beyond the Standard Model of particle physics. Large neutrino detectors and cosmological observations provide more and more information about neutrino masses and mixing angles, and might soon converge toward a self-consistent description with precisely measured parameters. The origin of neutrino masses remains mysterious, however, with a seemingly unlimited number of possible models flooding the literature. I will discuss ways to potentially distinguish certain classes of models and how to render a neutrino-mass theory predictive by connecting it to other anomalous observables such as the muon’s magnetic moment or CDF’s W-boson mass.

VIDEO:
Colloquium
Friday, January 27, 2023
3:30 PM
Clark Hall, Room 108
Note special room.

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


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