Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session B14: Dynamics of Black Holes |
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Sponsoring Units: GGR Chair: John Friedman, University of Wisconsinâ€“Milwaukee Room: Washington 4 |
Saturday, February 13, 2010 10:45AM - 10:57AM |
B14.00001: A study of non-linear effect in the ringdown of black holes in binary collisions Manuel Tiglio, David Brizuela, Frank Herrmann, Jose Maria Martin-Garcia, Enrique Pazos A complete gauge invariant formalism for arbitrary second order perturbations of Schwarzschild black holes will be presented. We will then discuss numerical simulations using that formalism to study non-linear effects in the ringdown of Schwarzschild black holes due to mode-mode coupling and the dependence of these effects on the type and shape of initial perturbation. Finally we will compare results with numerical simulations of colliding binary black holes in their late stage (ringdown) phase. [Preview Abstract] |
Saturday, February 13, 2010 10:57AM - 11:09AM |
B14.00002: Statistical Studies of Post Newtonian Equations Frank Herrmann, Chad Galley, Gustavo Guerberoff, John Silberholz, Manuel Tiglio We report on a statistical study of Post-Newtonian equations which we performed using Graphics Processing Units (GPUs). We find a number of interesting structures in the inspiral parameter space. The use of GPUs can provide a significant speed improvement over traditional CPU based approaches and can be efficiently utilized to study GR with its typically arithmetically intensive computations. [Preview Abstract] |
Saturday, February 13, 2010 11:09AM - 11:21AM |
B14.00003: Dynamics of Compact Binaries in Effective Field Theory Formalism Delphine Perrodin Coalescing compact binaries are predicted to be powerful emitters of gravitational waves, and provide a strong gravity environment ideal for the testing of gravity theories. We study the gravitational dynamics in the early inspiral phase of coalescing compact binaries using Non-Relativistic General Relativity (NRGR) - an effective field theory formalism based on the Post-Newtonian approximation to General Relativity, but which provides a consistent lagrangian framework and a systematic way in which to study binary dynamics and gravitational wave emission. We calculate in this framework the spin-orbit correction to the newtonian potential at 2.5 PN. [Preview Abstract] |
Saturday, February 13, 2010 11:21AM - 11:33AM |
B14.00004: Bobbing and Kicks in Electromagnetism and Gravity Samuel E. Gralla, Abraham I. Harte, Robert M. Wald We exploit the analogy between gravitation and electromagnetism to gain some insight into the origin and nature of ``bobbing motion'' and momentum ``kicks'' that occur in the merger of black hole binaries with spin. Specifically, we consider two charged magnetic dipoles in a slow-motion approximation, and examine the role that field momentum plays in their motion. As expected, there is significant exchange of momentum between field and bodies during bobbing. However, the bodies store this momentum as ``hidden mechanical momentum'' rather than center-of-mass velocity. In fact, the center-of-mass bobbing is entirely caused by a ``purely kinematical'' spin-acceleration effect that has nothing to do with electromagnetism (or gravity). A spinning binary will bob regardless of the source of acceleration, whereas the presence of a kick requires a release of field momentum. We conclude that the kick is not an inertial continuation of the bobbing. [Preview Abstract] |
Saturday, February 13, 2010 11:33AM - 11:45AM |
B14.00005: Gravitational self-force for a particle in circular orbit around the Schwarzschild black hole Abhay Shah, John Friedman, Tobias Keidl, Larry Price This talk reports recent progress on computing the self-force in a radiation gauge.The Weyl scalars determine the perturbed metric only up to a type D perturbation, and Carter's theorem is not sufficient to rule out a local perturbed Kerr-NUT or C-metric contribution to the singular field. Nevertheless, we show that only infinitesimal changes in mass and angular momentum arise and present alternative methods for obtaining the renormalized field for these contributions in a Schwarzschild and Kerr background. We present a corrected computation of the conservative part of the self-force in a radiation gauge for a particle circling a Schwarzschild black hole. The Weyl scalar and its derivatives are renormalized by subtracting the singular field to leading and sub-leading order from the retarded solution to the Bardeen-Press (Teukolsky) equation. Higher powers of l are subtracted by matching the retarded field with a series in l at high l. From the renormalized Weyl scalar (and its derivatives), one computes the renormalized Hertz potential (and its derivatives) by an algebraic inversion. From the renormalized Hertz potential and a renormalization of the l=0 and l=1 parts of the metric, we obtain the self-force. [Preview Abstract] |
Saturday, February 13, 2010 11:45AM - 11:57AM |
B14.00006: Higher order self-force effects Chad Galley We present recent progress towards understanding the impact and role of higher order self-force corrections on physically relevant quantities in extreme mass ratio inspirals. As an example, we study the motion of a scalar charge interacting with a nonlinear scalar field (that is motivated from general relativity) in a background black hole spacetime. We use the effective field theory (EFT) approach to perturbatively calculate the self-forced motion of the body and the wave generation through second order in the expansion parameter. Also, by including all particle-field interactions consistent with the symmetries of the theory we use the EFT approach to study the effects due to the finite but small size of the body. [Preview Abstract] |
Saturday, February 13, 2010 11:57AM - 12:09PM |
B14.00007: Gravitational Self-force in a Radiation Gauge: Circular Orbits in the Schwarzschild Spacetime Tobias Keidl, John Friedman, Larry Price, Abhay Shah In this talk, I discuss current progress in computing the self-force of a perturbation caused by a particle in circular orbit in Schwarzschild. This talk will focus on the developing the formalism necessary. Using only a single Weyl component of the perturbation, we generate a Hertz potential and use this to calculate the perturbed metric and self-force. [Preview Abstract] |
Saturday, February 13, 2010 12:09PM - 12:21PM |
B14.00008: Time--domain 2+1D Lorenz gauge self force and orbital evolution for EMRIs: progress report Kristen A. Lackeos, Leor Barack, Gaurav Khanna, Lior M. Burko We report on progress made in the calculation of the self force taking the approach of time--domain evolutions in 2+1D in the Lorenz gauge. We encounter several kinds of numerical instabilities: (a) dynamical instability near the black hole's event horizon that comes about because of the inadequacy of Boyer--Lindquist coordinates, and (b) uncontrolled growth of Lorenz gauge violating modes. We address type (a) instabilities with a transformation to a different coordinate system that cures the dynamical problem, and type (b) instability by the introduction of Lorenz gauge damping terms in the evolution equations. We also use previous results for the self force to drive the orbital evolution, and compare with the counterpart evolution obtained by monitoring fluxes and updating the orbit based on global conservation laws. [Preview Abstract] |
Saturday, February 13, 2010 12:21PM - 12:33PM |
B14.00009: Harmonic (Lorenz) Gauge Perturbations of the Schwarzschild Metric Mark Berndtson The satellite observatory LISA will be capable of detecting gravitational waves from extreme mass ratio inspirals (EMRIs), such as a small black hole orbiting a supermassive black hole. The gravitational effects of the much smaller mass can be treated as the perturbation of a known background metric, here the Schwarzschild metric. The perturbed Einstein field equations form a system of ten coupled partial differential equations. We solve the equations in the harmonic gauge, usually called the Lorenz gauge or Lorentz gauge. Using separation of variables and Fourier transforms, we write the solutions in terms of six radial functions which satisfy decoupled ordinary differential equations. The six functions are the Zerilli and five generalized Regge-Wheeler functions of spin s=2, 1 or 0. We then use the solutions to calculate the gravitational self-force for circular orbits. The self-force gives the first order perturbative corrections to the equations of motion. This talk is based mainly on unpublished thesis work, which is online at arxiv.org (gr-qc 0904.0033). [Preview Abstract] |
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