Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session Q8: Numerical Relativity: Black-Hole Binaries |
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Sponsoring Units: GGR Chair: Geoffrey Lovelace, Cornell University Room: Embassy B |
Monday, April 2, 2012 10:45AM - 10:57AM |
Q8.00001: Including Realistic Tidal Deformations in Binary-Black-Hole Initial Data Tony Chu A shortcoming of current binary-black-hole initial data is their contamination by spurious gravitational radiation, or ``junk'' radiation, that is not astrophysically relevant. This is a consequence of an oversimplified modeling of the binary's physics, which leads to an initially incorrect geometry that must relax during an evolution. This junk radiation that is generated in the process limits the accuracy of the actual gravitational waveforms of interest. There have been several efforts to address this issue by including more realistic outgoing gravitational radiation content in the initial data, although they did not fully satisfy the Einstein constraints. In this talk I focus on a complementary approach to improve the geometry near the black holes by including more realistic tidal deformations, while also satisfying the Einstein constraints. [Preview Abstract] |
Monday, April 2, 2012 10:57AM - 11:09AM |
Q8.00002: Spin-Spin Effects in Models of Binary Black Hole Systems Scott Hawley, Richard Matzner, Lindsey Thompson We have implemented a parallel multigrid solver, to solve the initial data problem for 3 + 1 General Relativity. This involves solution of elliptic equations derived from the Hamiltonian and the momentum constraints. We use the conformal transverse-traceless method of York and collaborators which consists of a conformal decomposition with a scalar that adjusts the metric, and a vector potential that adjusts the longitudinal components of the extrinsic curvature. The constraint equations are then solved for these quantities such that the complete solution fully satisfies the constraints. We apply this technique to compare with theoretical expectations for the spin-orientation- and separation-dependence in the case of spinning interacting (but not orbiting) black holes. We write out a formula for the effect of the spin-spin interaction which includes a result of Wald as well as additional effect due to the rotation of the mass quadrupole moment of a spinning black hole. [Preview Abstract] |
Monday, April 2, 2012 11:09AM - 11:21AM |
Q8.00003: Alternatives to Standard Puncture Initial Data for Binary Black Hole Evolution George Reifenberger, Wolfgang Tichy Standard Puncture initial data has been widely used for numerical analysis of black hole evolution despite it's shortcomings, most notably the inherent lack of gravitational radiation existing prior to the start of any simulation. We present two initial data schemes for binary black hole evolution as alternatives to the Standard Puncture approach. Both alternatives are based on Post-Newtonian expansions that contain realistic gravitational waves. The first scheme is based on a Post-Newtonian expansion in ADMTT gauge that has been resummed to approach Standard Puncture data at the black holes. The second alternative is obtained through asymptotic matching of the 4-metrics of two tidally perturbed Schwarzschild solutions to a second-order Post-Newtonian expansion in harmonic gauge away from the black holes. When evolved, both alternatives show gravitational radiation from the onset of the evolution. Current deficiencies compared to Standard Puncture data include more eccentric trajectories during inspiral and larger violation of the constraints, for which adherence has not been enforced. The deficiencies seem to be coupled, and we expect the initial data can be further improved once the constraints are enforced. [Preview Abstract] |
Monday, April 2, 2012 11:21AM - 11:33AM |
Q8.00004: New Conformally Flat Initial Data for Spinning Black Holes Yosef Zlochower, Carlos Lousto, Hiroyuki Nakano, Manuela Campanelli, Bruno Mundim We study conformally-flat initial data for an arbitrary number of spinning black holes with exact analytic solutions to the momentum constraints that combine the classical Bowen-York solution with the conformal Kerr extrinsic curvature by taking a weighted average of the Kerr and Bowen-York extrinsic curvatures, and varying the weight. We find that the curvature leading to the largest intrinsic spin, i.e. $\alpha=S/M^2_{\rm ADM}$, is neither the Kerr nor the Bowen-York extrinsic curvatures, but lies in between the two. We obtain a maximum intrinsic spin of $\alpha_{\rm max}=0.9324$. We present formulas for this new extrinsic curvature in a way that is as straightforward to code in a numerical initial data solver as the Bowen-York extrinsic curvature. [Preview Abstract] |
Monday, April 2, 2012 11:33AM - 11:45AM |
Q8.00005: Hangup Kicks: Still Larger Recoils by Partial Spin/Orbit Alignment of Black-Hole Binaries Carlos Lousto, Yosef Zlochower We revisit the scenario of the gravitational radiation recoil acquired by the final remnant of a black-hole-binary merger by studying a set of configurations that have components of the spin both aligned with the orbital angular momentum and in the orbital plane. We perform a series of 42 new full numerical simulations for equal-mass and equal-spin-magnitude binaries. We extend previous recoil fitting formulas to include nonlinear terms in the spins and successfully include both the new and known results. The new predicted maximum velocity approaches 5000km/s for spins partially aligned with the orbital angular momentum, which leads to an important increase of the probabilities of large recoils in generic astrophysical mergers. We find non-negligible probabilities for recoils of several thousand km/s from accretion-aligned binaries. [Preview Abstract] |
Monday, April 2, 2012 11:45AM - 11:57AM |
Q8.00006: Effects of nearly extremal black-hole spin in numerical-relativity simulations Geoffrey Lovelace There is a significant possibility that nearly extremal black holes (i.e., holes spinning nearly as rapidly as possible) exist and thus are among the compact-binary mergers that could be observed by Advanced LIGO. Numerical-relativity simulations of merging compact objects---necessary for predicting the gravitational waveforms that Advanced LIGO could detect---are particularly challenging when they contain nearly extremal black-hole spins. In this talk, I will discuss results from recent simulations [performed using the SpEC code (black-holes.org/SpEC)] that contain nearly extremal black holes, including a simulation of merging black holes with the highest spins (and among the most gravitational-wave cycles) simulated to date. In particular, I will compare the numerical gravitational waveforms and the holes' masses and spins with analytic predictions. I will also discuss the behavior of the strongly warped spacetime near the holes' horizons. [Preview Abstract] |
Monday, April 2, 2012 11:57AM - 12:09PM |
Q8.00007: Towards mass-production of binary black hole simulations Abdul Mroue, Harald Pfeiffer Numerical simulations of black hole binaries (BH-BH) have matured at an astonishing rate over the last years. Nevertheless, there is a pronounced dearth of accurate simulations covering many inspiral orbits for precessing BH-BH binaries. This talk reports on an effort to significantly increase the number of high-quality BH-BH waveforms using the Spectral Einstein code (black-holes.ord/SpEC). We will describe our approach to efficiently compute low-eccentricity orbital parameters, detail our current set of simulations, and present first scientific results from these simulations, focusing on the inspiral phase of the BH-BH. [Preview Abstract] |
Monday, April 2, 2012 12:09PM - 12:21PM |
Q8.00008: BH-BH mergers, ringdowns and wave-forms in a mass-production environment Bela Szilagyi The Caltech-Cornell-CITA Spectral Einstein Code has, in the past years, matured to the point where the simulation of the full binary black hole problem (inspiral, merger, ringdown) ceases to require a significant amount of human interaction. This, combined with the low CPU-hour cost of these runs, allows SpEC to enter ``mass-production mode.'' I will discuss some of the technicalities involved in obtaining a robust algorithm. I will present measures of code accuracy in this mass-production context, as seen in the black hole physical characteristics as well as the wave-forms. [Preview Abstract] |
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