Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session H16: Numerical Modeling of Binary Black HolesLive

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Sponsoring Units: DGRAV Chair: Pablo Laguna, Univ. of Texas  Austin 
Sunday, April 18, 2021 10:45AM  10:57AM Live 
H16.00001: Gravitational Memory in Numerical Relativity: Computing Memory Effects and Correcting Existing Waveforms Keefe Mitman, Dante A. B. Iozzo, Neev Khera, Michael Boyle, Tommaso De Lorenzo, Nils Deppe, Lawrence E. Kidder, Jordan Moxon, Harald Pfeiffer, Mark Scheel, Saul Teukolsky, William Throwe Gravitational memory is a phenomenon induced by the passage of gravitational waves that corresponds to persistent, physical changes to spacetime. We present advances in resolving the two primary gravitational memory effectsdisplacement and spin memoryin numerical simulations of binary black hole mergers produced by SXS's Spectral Einstein Code. We show that the waveforms extracted using Cauchycharacteristic extraction (CCE) obey the BondiMetznerSachs (BMS) balance laws to a high degree of accuracy, unlike previous waveforms produced by numerical relativity simulations. We also show that the waveforms in all publicly available waveform catalogs, which do not exhibit memory effects, can be corrected to include such features. [Preview Abstract] 
Sunday, April 18, 2021 10:57AM  11:09AM Live 
H16.00002: Ultimate Fate of Apparent Horizons During a Binary Black Hole Merger Ivan Booth, Robie Hennigar, Daniel PookKolb During a binary black merger, event horizons evolve via the ``pair of pants’’ diagram. This has now been understood for five decades. However the full equivalent diagram for apparent horizons, and in particular the ultimate fate of the original apparent horizon of each black hole, remained unresolved. Very recently, significant progress has been made on this problem. In this talk I will present the complete evolution of the horizons traced out by all marginally outer trapped surfaces (MOTS) during an axisymmetric black hole merger. The evolution is much more interesting and intricate than that for event horizons. The progress was made possible by the application of new MOTSfinding techniques and the behaviours of the various horizons is elucidated by an analysis of the MOTS stability spectrum. [Preview Abstract] 
Sunday, April 18, 2021 11:09AM  11:21AM Live 
H16.00003: Progress toward the first simulations of binary black holes holes with SpECTRE Geoffrey Lovelace Numericalrelativity calculations of binary black holes are crucial tools for modeling and interpreting gravitationalwave observations. Future gravitationalwave observatories on Earth and in space will require waveform models that are much more accurate than numerical relativity can currently achieve. SpECTRE is a nextgeneration numericalrelativity code that aims to achieve much greater accuracy than is possible today, by employing techniques such as adopting a Discontinuous Galerkin method and taskbased parallelism. In this talk, I will discuss progress toward SpECTRE's first simulations of merging black holes. [Preview Abstract] 
Sunday, April 18, 2021 11:21AM  11:33AM Live 
H16.00004: Calculating apparenthorizon quantities with SpECTRE, a nextgeneration numerical relativity code. Marlo Morales, Geoffrey Lovelace SpECTRE is a nextgeneration numericalrelativity code (currently under development) that will calculate the gravitational waves emitted by colliding black holes and neutron stars with unprecedented accuracy, by using novel techniques that enable it to scale to hundreds of thousands of compute cores. These highaccuracy calculations will help scientists interpret observations from nextgeneration gravitationalwave detectors. I will discuss the completion of SpECTRE's computational infrastructure to measure the properties of black hole's horizons, such as the black hole's masses and spin angular momenta, which are especially important for connecting the calculations to observations. Specifically, I will present results assessing the accuracy that SpECTRE is able to achieve, and I will compare the results to those from the Spectral Einstein Code (SpEC), a currentgeneration numerical relativity code. [Preview Abstract] 
Sunday, April 18, 2021 11:33AM  11:45AM Live 
H16.00005: Long and highly accurate eccentric binary black hole simulations with SpEC Antoni RamosBuades, Hannes Rueter, Harald Pfeiffer Generic binary black hole (BBH) mergers may occur in elliptical orbits with nonzero eccentricity. The waveform models used by the LIGO and Virgo collaboration so far to detect and estimate parameters of gravitational wave (GW) signals are based on the assumption of quasicircular orbits. In the recent years there has been an increasing effort from the GW community to model eccentric BBHs. The first step required to model such systems is the generation of a data set of eccentric numerical relativity (NR) simulations which can be used to calibrate and validate the eccentric waveform models, and test data analysis implications for such waveforms. First, the state of art of the current eccentric NR data sets will be reviewed. Next, we will show the adaption of the spectral NR code, SpEC, to produce a set of long and highly accurate eccentric nonspinning NR simulations from mass ratio 1 to 10. The accuracy of these new waveforms is assessed by showing convergence tests and computing the unfaithulness between waveforms at different resolutions. Finally, we briefly show possible applications of these longer and more accurate waveforms to waveform modelling or data analysis studies, like parameter estimation or searches. [Preview Abstract] 
Sunday, April 18, 2021 11:45AM  11:57AM Live 
H16.00006: BlackHoles@Home: Numerical Relativity on ConsumerGrade Computers, for the Benefit of Gravitational Wave Astronomy Zachariah Etienne Much of gravitational wave (GW) science depends on GW observations being compared with millions of theoretical predictions generated by GW approximants. Our most reliable approximants are built upon GW catalogs extracted from numerical relativity (NR) simulations, which solve Einstein's equations in full. To date each of these NR simulations has required a small computing cluster, which has limited throughput to only about 3,000 GWs in 15 years. Given the vast parameter space of even the simplest observed GW sourcebinary black holes (BBHs)such a small GW collection threatens potential science gains from future GW observations. BlackHoles@Home is a proposed BOINCbased citizenscience project leveraging new techniques to fit NR BBH simulations on a consumergrade desktop computer, enabling GW followups and catalogs with unprecedented throughput using volunteer computers. We recently demonstrated that our techniques enable the final orbits of a BBH and postmerger to be calculated on a cellphone in full NR, with accurate GWs. We report on our latest improvements, which indicate we are on track to launch BlackHoles@Home within months. [Preview Abstract] 
Sunday, April 18, 2021 11:57AM  12:09PM Live 
H16.00007: Gravitational recoil in black hole mergers inside scalar field clouds Miguel Gracia, YuPeng Zhang, Pablo Laguna The loss of linear momentum carried away by gravitational waves in the coalescence of binary black holes inflicts a kick on the final black hole. The effect has been mostly studied for black holes merging in vacuum. We investigate the kick on the final black hole when the binary is immersed in a cloud of scalar field. We present results from two types of binaries: nonspinning, unequalmass systems and systems with equal mass holes with antialigned spins perpendicular to the orbital plane. We find that the scalar field attenuates the kick of the final remnant black hole in all the studied cases. [Preview Abstract] 
Sunday, April 18, 2021 12:09PM  12:21PM Live 
H16.00008: Adapted gauge to a quasilocal measure of the black holes recoil Nicole Rosato, Carlos Lousto, James Healy We explore different gauge choices in the moving puncture formulation in order to improve the accuracy of a linear momentum measure evaluated on the horizon of the remnant black hole produced by the merger of a binary.In this talk, we will investigate gauges in which the parameter $m\eta$, which damps oscillations in the shift equation, takes on decreasing constant values. These alternative gauges are used to do an indepth study of a $q=m_2/m_1=1/3$ binary in which it is determined that choosing an $m\eta$ at 1 produces the most accurate measure of recoil velocity when compared to the evaluation of the radiated linear momentum at infinity for typical numerical resolutions.This result is then confirmed with alternative comparablemass, nonspinning binaries$q=1/2$ and $q=1/5$ as well as an equal mass binary with dimensionless spin of 0.8. [Preview Abstract] 
Sunday, April 18, 2021 12:21PM  12:33PM On Demand 
H16.00009: Simulating binary black hole systems with intermediate mass ratios Eric Hirschmann, Milinda Fernando, David Neilsen, Hari Sundar, Yosef Zlochower Binary black hole systems with constituents that have very different masses are a subset of the binary population that, from a computational perspective, are more challenging to simulate than equal or near equal mass binaries. Their resource demands are significant and it is broadly understood that their successful evolution will require particular approaches and methods that are tuned to this region of the parameter space. We combine two such approaches, namely a parallel octreerefined adaptive mesh and a wavelet adaptive multiresolution method to produce the mesh. This highly scalable framework permits the efficient and rapid simulation of such intermediate mass ratio inspirals (IMRIs). We present some results from these efforts that have proven successful in simulating binaries with larger mass ratios. [Preview Abstract] 
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