Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session Q16: Numerical Modeling of Binary Black HolesOn Demand

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Sponsoring Units: DGRAV Chair: Jorge Pullin, Louisiana State University Room: Virginia C 
Monday, April 20, 2020 10:45AM  10:57AM On Demand 
Q16.00001: High massratio binary black hole simulations in numerical relativity Matthew Giesler, Mark Scheel, Vijay Varma, Saul Teukolsky We present high accuracy, fully nonlinear, numerical simulations of binary black holes up to a mass ratio of $q=30$. Using improved methods, we extend the capabilities of the numerical relativity code, SpEC, to simulate binary black holes with mass ratios beyond its previous limit of $q=10$. Such systems are potential sources for current gravitational wave detectors (i.e. LIGO) and are expected to be even more promising for future spacebased detectors (e.g. LISA). The binaries are evolved through a minimum of $14$ orbits, providing a sufficient number of gravitational wave cycles to compare with predictions from approximate models. We present comparisons of our numerical waveforms with selfforce predictions, the most promising perturbative scheme for extreme mass ratio inspirals. Additionally, we compare our waveforms with effectiveonebody (EOB) approximants, which model the full waveform and are presumed to be valid at any mass ratio. [Preview Abstract] 
Monday, April 20, 2020 10:57AM  11:09AM Not Participating 
Q16.00002: Evolving 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 large mass ratios. [Preview Abstract] 
Monday, April 20, 2020 11:09AM  11:21AM On Demand 
Q16.00003: Revisiting the QuasiKinnersley Tetrad in Numerical Relativity Nicole Rosato, James Healy, Carlos Lousto We present a method of constructing rotation parameters $a$ and $b$ for performing Type I and Type II transformations of Weyl scalars $\Psi_a$ into the quasiKinnersley frame. This frame is transverse ($\Psi_1=\Psi_3=0$) and should have $\Psi_2 \to \sqrt{\mathcal{I}/3}$ asymptotically, where $\mathcal{I}$ is a spacetime invariant. This frame better represents physical properties of the spacetime, such as outgoing gravitational radiation. Using the quasiKinnersley frame, we study an index $\mathcal{D}$ that, in conjuction with the $\mathcal{S}$ invariant, measures the deviations from Petrov Type D of a BBH system in the strongfield region. $\mathcal{D}$ is invariant under Type II and III rotations, but not under Type I. Studying this index will tell us more accurately how far a BBH spacetime deviates from Type D. This index is used in numerical simulations of BBH systems to investigate the Petrov Type in the Strong Field region during the final inspiral and merger phases. This talk will also discuss how the gravitational wave scalar $\Psi_4$ in the quasiKinnersley frame can be used to extract gravitational radiation. Since the QK $\Psi_4$ is an accurate representation of outgoing radiation, waveforms can be extracted close to the BBH system, reducing computational expense. [Preview Abstract] 
Monday, April 20, 2020 11:21AM  11:33AM Not Participating 
Q16.00004: Resolving Gravitational Memory in Numerical Relativity using Cauchycharacteristic Extraction Keefe Mitman, Saul Teukolsky, Mark Scheel, Jordan Moxon Although gravitational memory was realized in the 1970s, numerical simulations of binary black hole mergers have been unable to resolve this phenomenon until now. We show that by using Cauchycharacteristic extraction (CCE) to extract waveforms in simulations produced by SXS's Spectral Einstein Code, we can accurately resolve the gravitational memory. We present results for memory in simulations with a variety of mass ratios and spins. We also discuss the measurability of memory for both LIGO and LISA. [Preview Abstract] 
Monday, April 20, 2020 11:33AM  11:45AM Not Participating 
Q16.00005: Boosting spinweighted spherical harmonics Michael Boyle Scalar spherical harmonics form the backbone of analysis of radiating fields in elementary physics. Extending such analyses to describe radiating tensor fields, gravitationalwave and CMB astronomers typically use ``spinweighted'' spherical harmonics, which account more completely for the properties of those tensors under rotation. I will describe the appropriate framework for understanding these harmonics, as well as generalizations that will allow us to account for the properties under more general Lorentz transformations, and how this can lead to more efficient representations of the gravitational and electromagnetic fields. [Preview Abstract] 
Monday, April 20, 2020 11:45AM  11:57AM On Demand 
Q16.00006: Efficient simulations of single highspin black holes with a new gauge condition Yitian Chen Highspin binary black hole (BBH) simulations are computationally expensive. As the spin increases, the region where an excision surface can be placed becomes narrower. This makes the evolutions even more demanding because of the accuracy required to be able to find a suitable excision surface. We explore a new gauge condition for generalized harmonic systems to broaden the region where the excision surface is placed, and present preliminary results from evolutions of a single highspin black hole. Our objective is the application of this new gauge condition to highspin BBH evolutions. [Preview Abstract] 
Monday, April 20, 2020 11:57AM  12:09PM Not Participating 
Q16.00007: Generalrelativistic simulations of quasicircular inspirals of charged black holes Gabriele Bozzola, Vasileios Paschalidis The electric charge is a parameter often neglected in generalrelativistic simulations of black holes. As a result, little is known about the dynamics of charged binary black holes in the latest stages of their inspiral. In this talk, we present our first numericalrelativity simulations of quasicircular mergers of these systems. Using a $3+1$ formalism, we obtained fully selfconsistent solutions of EinsteinMaxwell's equations, and extracted the electromagnetic and gravitational output. We will discuss what LIGOVirgo observations of mergers of binary black holes and the (non)detections of electromagnetic counterparts can teach us about the charge of astrophysical black holes. [Preview Abstract] 
Monday, April 20, 2020 12:09PM  12:21PM Not Participating 
Q16.00008: Black hole binaries: Ergoregions, photon surfaces, wave scattering, and quasinormal modes Thiago Assumpcao, Vitor Cardoso, Akihiro Ishibashi, Mauricio Richartz, Miguel Zilhao In this talk, we address the computationally intense task of numerical modeling of black hole (BH) binaries by focusing on simple geometries that are static and, therefore, never merge. Two different binary models are used to investigate null closed orbits and their response to external perturbations. The first system is the MajumdarPapapetrou (MP) solution, which describes a static configuration of an arbitrary number of maximally charged black holes. We focus on the special case of two MP black holes and investigate some of its properties, such as the different types of closed photon orbits and the instability scale of unstable circular orbits. The second system comes from Analogue Models of Gravity, which rely on the mathematical relationship between perturbations in fluids and scalar perturbations in curved spacetimes. In this work, we use a doublesink solution of the fluid equations and explore an analogy with the MP geometry. We show that the ergoregion of the doublesink geometry does not coincide with the event horizon, which raises the possibility of superradiant scattering and Penroselike processes in more realistic astrophysical systems. [Preview Abstract] 
Monday, April 20, 2020 12:21PM  12:33PM On Demand 
Q16.00009: Kicking gravitational wave detectors with recoiling black holes Carlos Lousto, James Healy Binary black holes emit gravitational radiation with net linear momentum leading to a retreat of the final remnant black hole that can reach up to $\sim5,000$ km/s. Full numerical relativity simulations are the only tool to accurately compute these recoils since they are largely produced when the black hole horizons are about to merge and they are strongly dependent on their spin orientations at that moment. We present eight new numerical simulations of BBH in the hangupkick configuration family, leading to the maximum recoil. Black holes are equal mass and near maximally spinning ($\vec{S}_{1,2}/m_{1,2}^2=0.97$). Depending on their phase at merger, this family leads to $\sim\pm4,700$ km/s and all intermediate values of the recoil along the orbital angular momentum of the binary system. We introduce a new invariant method to evaluate the recoil dependence on the merger phase via the waveform peak amplitude used as a reference phase angle and compare it with previous definitions. We also compute the mismatch between these hangupkick waveforms to infer their observable differentiability by gravitational wave detectors, such as advanced LIGO, finding currently reachable signaltonoise ratios, hence allowing for the identification of highly recoiling black holes. [Preview Abstract] 
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