In this talk I will discuss recent work on numerically solving for the binary black hole dynamics of black holes in Einstein scal ar Gauss-Bonnet (ESGB) gravity. This modified gravity theory can be motiva ted by effective field theory reasoning\, and admits scalarized black hole solutions. These two facts make it a promising theory to constrain using binary black hole\, gravitational wave observations. I will discuss how re cent advances in mathematical relativity--in particular\, the development of the "\;modified harmonic formulation"\;--have opened up the pos sibility of constructing fully nonlinear solutions to the equations of mot ion of ESGB gravity (in addition to a class of scalar-tensor modified theo ries known as "\;Horndeski"\; theories). I will discuss numerical simulations of single and binary black hole systems in these theories\, an d the gravitational and scalar radiation they emit.\n DTSTART:20210208T180000Z LOCATION:Online\, Room Zoom SUMMARY:The classical evolution of binary black hole systems in scalar-tens or theories END:VEVENT BEGIN:VEVENT DESCRIPTION:Alejandro Cardenas-Avendano\, University of Illinois Urbana-Cha mpaign\n\n

Over the past years\, electromagne tic and gravitational observations have been used to understand the nature of black holes and the material around them. Our ability to learn about t he underlying physics\, however\, depends heavily on our understanding of the gravity theory that describes the geometry around these compact object s\, and for the electromagnetic observations\, also on the complex astroph ysics that produces the observed radiation. In this talk\, I will discuss our current ability to constrain and detect deviations from general relati vity using (i) the electromagnetic radiation emitted by an accretion disk around a black hole\, and (ii) the gravitational waves produced when compa rable-mass black holes \;collide\, and when a small compact object fal ls into a supermassive one in an extreme mass-ratio inspiral. I will also compare the constraining capabilities of these two types of observations t o show how current gravitational wave observations have already placed con straints on possible modifications to general relativity\, that are more s tringent than what can be achieved with current and near-future electromag netic observations.

\n DTSTART:20210222T180000Z LOCATION:Online\, Room Zoom SUMMARY:Testing the Schwarzschild/Kerr black hole hypothesis with gravitati onal and electromagnetic waves END:VEVENT BEGIN:VEVENT DESCRIPTION:Justin Vines\, Max Planck Institute for Gravitational Physics ( Albert Einstein Institute)\n\nThe detection and analysis of gravitational wave signals from coalescing binary systems crucially relies on analytic perturbative a pproaches to the two-body problem in general relativity (as well as on num erical approaches). \; While the post-Newtonian (weak-field and slow-m otion) approximation is most directly relevant to observations by LIGO et al.\, recent developments have revived interest in the more inclusive post -Minkowskian (weak-field but arbitrary-speed) approximation -- particularl y in relation to highly advanced techniques developed by particle physicis ts for computing relativistic quantum scattering amplitudes and associated classical observables. \; This interplay between high-energy quantum physics and gravitational-wave science has led to several new results and useful insights\, particularly regarding relationships between complimenta ry approximation schemes\; this importantly also includes the "\;self- force"\; or "\;post-test-body"\; approach\, treating small mas s ratios but arbitrary field strengths and speeds. \; We will review s ome of these developments\, focusing on the post-Minkowskian treatment of the spinning black hole binary problem.

\n DTSTART:20210308T180000Z LOCATION:Online\, Room Zoom SUMMARY:Recent developments in the post-Minkowskian approach to the spinnin g black hole binary problem END:VEVENT BEGIN:VEVENT DESCRIPTION:Paul Lasky\, Monash University\n\nSince the first gravitational-wave detecti on of a binary black hole merger in 2015\, the LIGO and Virgo detectors ha ve observed gravitational waves from more than 50 merging systems. That nu mber is expected to increase significantly over the coming years as these experiments become even more sensitive. The increased number of detections \, and the improved sensitivity of these instruments\, allows us to probe the ultra-strong regime of gravity\, as well as the formation history of t hese systems. I will discuss ongoing efforts to test general relativity in the ultra strong-field regime\, including tests of the no-hair theorem an d searches for gravitational-wave memory -- a permanent deformation of spa cetime following the passage of a gravitational wave. I will also discuss& nbsp\;efforts to detect orbital eccentricity in these systems\, which has led to potentially the first observation of a second-generation black hole merger.

\n DTSTART:20210322T220000Z LOCATION:Online\, Room via Zoom SUMMARY:Adventures in Gravitational-wave Astronomy: testing for hair\, memo ry\, and eccentricity END:VEVENT BEGIN:VEVENT DESCRIPTION:Huan Yang\, Perimeter Institute and University of Guelph\n\n~~In this talk I will discuss relevant environmen
t effects (i.e.\, accretion disk\, tidal gravitational field from close ob
jects) that influence the formation and dynamics of extreme mass ratio ins
pirals (EMRIs)\, which are important sources for LISA. I will show that di
sk-assisted EMRIs may be more commonly seen by LISA. They can be distingui
shed from EMRIs formed through cluster multibody scattering by eccentricit
y measurements. The disk force and tidal gravitational field from nearby o
bjects may also leave observable imprints on the waveform of the EMRIs\, w
hich provide new opportunities in probing the stellar distributions and co
nstraining the accretion physics at galactic centers.~~~~
~~

\;

\n DTSTART:20210405T170000Z LOCATION:Online\, Room via Zoom SUMMARY:Formation and dynamics of extreme mass ratio inspirals with environ mental effects END:VEVENT BEGIN:VEVENT DESCRIPTION:Jordan Moxon\, California Institute of Technology\n\nNumerical relativity sta nds as the primary method of generating precise waveform predictions for c omparable-mass compact binary coalescences used in gravitational wave data analysis pipelines. \;To produce those predictions\, the spacetime i n the vicinity of the binary system must be simulated to high precision\, and then the waveform information must be extracted from the dynamical spa cetime near the binary. \;Cauchy Characteristic Evolution (CCE) offer s a wave extraction method capable of efficiently determining a complete\, asymptotically well-behaved metric at Scri+. \;For our implementatio n of CCE in SpECTRE\, we have developed a number of mathematical refinemen ts of the CCE system that improves spectral convergence and eases the comp utation of detailed dynamical spacetime information at Scri+. \;Our i mplementation in SpECTRE is far faster than previous CCE codes\, is free f rom logarithmic pathologies\, and computes full waveform information: news \, strain\, and all five Weyl scalars. \;I will discuss the numerical methods used to improve the performance of SpECTRE CCE\, as well as sever al projects that have used the system to study gravitational wave memory a nd other subtle waveform effects that become available with full access to waveform data at Scri+.

\n DTSTART:20210426T170000Z LOCATION:Online\, Room Zoom SUMMARY:High-performance Gravitational Wave Extraction in SpECTRE END:VEVENT BEGIN:VEVENT DESCRIPTION:(CANCELLED) Hsin-Yu Chen\, MIT - Massachusetts Institute of Tec hnology\n\nOver last six years\, the observa tion of gravitational-wave signals from compact binary mergers \;have significantly expanded our knowledge in physics and astronomy. In this tal k\, I will discuss what we learned in cosmology\, nuclear physics\, and he avy-elements production from LIGO-Virgo observations. I will then discuss the future aspects and a few challenges in these areas.

\n DTSTART:20210920T170000Z LOCATION:Physics Building\, Room 313 SUMMARY:Measurements with gravitational-wave observations: from the heavy m etals production to the Universe expansion END:VEVENT BEGIN:VEVENT DESCRIPTION:Dr. BĂ©atrice Bonga\, Radboud University\n\n~~Resonances are ubiquitous
in nature. In this talk\, I will focus on resonances due to the interactio
n of two black holes orbiting a central massive black hole. Such tidal res
onances will generically occur for EMRIs if nearby compact objects exist.
By probing their influence on the phase of the EMRI waveform\, we can in p
rinciple extract information about the environmental tidal field of the EM
RI system\, albeit at the cost of a more complicated EMRI waveform model.
I will also describe mean motion resonances\, which are a mechanism that c
an create the necessary conditions for tidal resonance to occur.~~

I will show how to derive analytic gravitational waveforms associated to the coalescence of a &ldquo \;hairy&rdquo\; black hole binary in Einstein-scalar-Gauss-Bonnet gravity (ESGB). I will present the ESGB post-Newtonian (PN) Lagrangian and gravita tional wave fluxes. The PN framework relies on \;reducing the black ho les to point particles with scalar-field-dependent masses. In light of the first law of thermodynamics of ESGB black holes\, I will show that \; this procedure amounts to fixing their Wald entropies. As a consequence\, inspiraling ESGB black holes can grow scalar &ldquo\;hair&rdquo\; until th ey turn into naked \;singularities. I will then extend the scope of th e PN approximation to the strong field regime near merger by generalizing the Effective-One-Body (EOB) \;formalism to ESGB gravity.

\n DTSTART:20211018T170000Z LOCATION:Online\, Room via Zoom SUMMARY:Gravitational radiation from a binary black hole coalescence in Ein stein-scalar-Gauss-Bonnet gravity END:VEVENT BEGIN:VEVENT DESCRIPTION:Professor Thomas Sotiriou \, The University of Nottingham\n\nIn general rela tivity black holes are fully characterised by their mass\, spin\, and elec tromagnetic charge. No-hair theorems indicate that scalar fields cannot af fect black hole spacetimes. However\, the devil is in the details and\, in practice\, no-hair theorems allow us to identify a list of interesting ex ceptions in which scalar field leave their imprint on black holes. Such sc enarios are of particular interest to gravitational wave searches for new fundamental physics. I will give an overview of how new fundamental scalar s affect black hole spacetimes and of how this can be imprinted on gravita tional wave observations.

\n DTSTART:20211101T170000Z LOCATION:Online\, Room via Zoom SUMMARY:Black hole hair: from no-hair theorems to scalarization END:VEVENT BEGIN:VEVENT DESCRIPTION:Leah Jenks \, Brown University\n\nIn this talk I will give an overview of recent and ongoing work \;regarding rotating black holes in dynamical Chern-Simons (dCS) gr avity. dCS gravity is a well motivated modified theory of gravity which ha s been extensively studied in gravitational and cosmological contexts. I w ill first discuss unique geometric structures\, `the Chern-Simons caps\,&# 39\; which slowly rotating black holes in dCS gravity were recently found to possess. Motivated by the dCS caps\, I will then discuss superradiance in the context of slowly rotating dCS black holes and show that there are& nbsp\;corrections to the usual solution for a Kerr black hole. Lastly\,&nb sp\;I will comment on the observable implications for these corrections an d point towards avenues for future work.

\n DTSTART:20211108T180000Z LOCATION:Online\, Room via Zoom SUMMARY:Aspects of Rotating Black Holes in Dynamical Chern-Simons Gravity END:VEVENT BEGIN:VEVENT DESCRIPTION:Venkatesa Chandrasekaran \, Institute for Advanced Study\n\nGravitational sub systems\, such as black holes\, are important objects of study in both cla ssical and quantum gravity. Insight into the gravitational degrees of free dom of a subsystem can be gained by analyzing the symmetries and charges o f gravity in the associated spacetime subregion. In this talk\, I will use the covariant phase space formalism to make progress on this problem in g eneral relativity\, with a particular focus on subregions bounded by null hypersurfaces\, such as event horizons or causal diamonds. Surprisingly\, on null surfaces the gravitational field will turn out to have infinitely many symmetries\, akin to the BMS symmetries at null infinity. In a comple tely general setting in which the subsystem can emit or absorb radiation\, I will then derive an infinite set of charges and conservation laws on th e null surface\, and explain their significance for physics deep in the gr avitational field. Finally\, I will describe progress towards an understan ding of black hole entropy through this formalism.

\n DTSTART:20211115T180000Z LOCATION:Online\, Room via Zoom SUMMARY:Symmetries and Charges of Gravitational Subsystems END:VEVENT BEGIN:VEVENT DESCRIPTION:Philippe Landry \, \n\n DTSTART:20211206T180000Z LOCATION:Physics Building\, Room 313 SUMMARY: END:VEVENT END:VCALENDAR