Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session R15: Gravitational Wave Theory |
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Sponsoring Units: GGR Chair: Nico Yunes, Montana State University Room: 251C |
Monday, April 18, 2016 10:45AM - 10:57AM |
R15.00001: Inspirals into Gargantua Niels Warburton, Samuel Gralla, Scott Hughes We model the inspiral of a compact, stellar mass object into a massive black hole rotating at or just below the theoretical maximum. We find that once the compact object enters the near-horizon regime the gravitational radiation is characterized by a constant frequency, equal to the horizon frequency, with an exponentially damped profile. This contrasts with the usual `chirping' behaviour of a black hole binary system and were such a waveform observed it would constitute a `smoking gun' for a (near) extremal black hole in nature. [Preview Abstract] |
Monday, April 18, 2016 10:57AM - 11:09AM |
R15.00002: Two Timescale Approximation Applied to Gravitational Waves from Eccentric EMRIs Jordan Moxon, Eanna Flanagan, Tanja Hinderer, Adam Pound Gravitational-wave driven inspirals of compact objects into massive black holes (Extreme Mass Ratio Inspirals - EMRIs) form an interesting, long-lived signal for future space-based gravitational wave detectors. Accurate signal predictions will be necessary to take full advantage of matched filtering techniques, motivating the development of a calculational technique for deriving the gravitational wave signal to good approximation throughout the inspiral. We report on recent work on developing the two-timescale technique with the goal of predicting waveforms from eccentric equatorial systems to subleading (post-adiabatic) order in the phase, building on recent work by Pound in the scalar case. The computation requires us to understand the dissipative component of the second-order self force. It also demands careful consideration of how the two timescale (near-zone) approximation should match with the post-Minkowski approximation of the gravitational waves at great distances. [Preview Abstract] |
Monday, April 18, 2016 11:09AM - 11:21AM |
R15.00003: Inspiralling, spinning, non-precessing binary black hole spacetime via asymptotic matching Brennan Ireland, Bruno Mundim, Hiroyuki Nakano, Manuela Campanelli We construct and present a new global, fully analytic, approximate spacetime which accurately describes the dynamics of non-precessing, spinning black hole binaries during the inspiral phase of the relativistic merger process. This approximate solution of the vacuum Einstein's equations can be obtained by asymptotically matching perturbed Kerr solutions near the two black holes to a post-Newtonian metric valid far from the two black holes. This metric is then matched to a post-Minkowskian metric even farther out in the wave zone. The procedure of asymptotic matching is generalized to be valid on all spatial hypersurfaces, instead of a small group of initial hypersurfaces discussed in previous works. This metric is well suited for long term dynamical simulations of spinning black hole binary spacetimes prior to merger, such as studies of circumbinary gas accretion which requires hundreds of binary orbits. [Preview Abstract] |
Monday, April 18, 2016 11:21AM - 11:33AM |
R15.00004: Tail Effects in Gravitational Wave Fluxes for Generic Eccentricity Nicholas Loutrel, Nicolas Yunes Gravitational wave tail effects result from the scattering of waves off of the spacetime curvature of the system that produced them. These tails modify the energy and angular momentum fluxes carried by gravitational waves to spatial infinity. The tail contributions to the fluxes have proven to be difficult to calculate analytically for generic eccentric orbits, with analytic results only available for binaries with small eccentricity. In this talk, I will describe a new technique that allows us to re-sum the tail enhancement factors for binaries with generic eccentricity by using the uniform asymptotic expansion of Bessel functions. [Preview Abstract] |
Monday, April 18, 2016 11:33AM - 11:45AM |
R15.00005: Highly eccentric inspirals into a Schwarzschild black hole using self-force calculations Thomas Osburn, Niels Warburton, Charles Evans Eccentric-orbit inspirals into a massive black hole are calculated using the gravitational self-force. Both extreme-mass-ratio inspirals (EMRIs) and intermediate-mass-ratio inspirals (IMRIs) are modeled. These calculations include all dissipative and conservative first-order-in-the-mass-ratio effects for inspirals into a Schwarzschild black hole. We compute systems with initial eccentricities as high as e = 0.8 and initial separations as large as 100 M. In the case of EMRIs, the calculations follow the decay through many thousands of orbits up to the onset of the plunge. Inspirals are computed using an osculating-orbits scheme that is driven by self-force data from a hybridized self-force code. A Lorenz gauge self-force code is combined with highly accurate flux data from a Regge-Wheeler-Zerilli code, allowing the hybrid self-force model to track orbital phase in the inspirals to within ~0.1 radians or better. Extensions of the method to include other physical effects are considered. [Preview Abstract] |
Monday, April 18, 2016 11:45AM - 11:57AM |
R15.00006: Eccentric orbit E/IMRI gravitational wave fluxes to 7PN order Erik Forseth, Charles R. Evans, Seth Hopper Knowledge of gravitational wave fluxes (energy and angular momentum, at both infinity and the horizon) from eccentric-orbit inspirals is extended from 3PN to 7PN order at lowest order in small mass ratio. Previous post-Newtonian eccentric-orbit results up to 3PN relative order are confirmed by our new black hole perturbation calculations. The calculations are based on Mano, Suzuki, and Takasugi (MST) analytic function expansions, and results are computed to 200 decimal places of accuracy using Mathematica. Over 1,700 distinct orbits were computed, each with as many as 7,000 Fourier-harmonic modes. A large number of PN coefficients between 3.5PN and 7PN orders were determined, either in exact analytic form or with accurate numerical values, in expansions in powers of a PN compactness parameter and its logarithm, and powers of eccentricity. We show a parametrization that removes singularities in the fluxes as the eccentricity approaches unity, thus making the expansions more convergent at high eccentricity. We also found (nearly) arbitrarily accurate expansions for the previously discussed 1.5PN, 2.5PN, and 3PN hereditary terms. [Preview Abstract] |
Monday, April 18, 2016 11:57AM - 12:09PM |
R15.00007: Canonical Hamiltonian for an extended test body in curved spacetime: To quadratic order in spin Justin Vines, Daniela Kunst, Jan Steinhoff, Tanja Hinderer We derive a Hamiltonian for an extended spinning test-body in a curved background spacetime, to quadratic order in the spin, in terms of three-dimensional position, momentum, and spin variables having canonical Poisson brackets. This requires a careful analysis of how changes of the spin supplementary condition are related to shifts of the body's representative worldline and transformations of the body's multipole moments, and we employ bitensor calculus for a precise framing of this analysis. We apply the result to the case of the Kerr spacetime and thereby compute an explicit canonical Hamiltonian for the test-body limit of the spinning two-body problem in general relativity, valid for generic orbits and spin orientations, to quadratic order in the test spin. This fully relativistic Hamiltonian is then expanded in post-Newtonian orders and in powers of the Kerr spin parameter, allowing comparisons with and extensions of the test-mass limits of available post-Newtonian results. Both the fully relativistic Hamiltonian and the results of its expansion can inform the construction of waveform models, especially effective-one-body models, for the analysis of gravitational waves from compact binaries. [Preview Abstract] |
Monday, April 18, 2016 12:09PM - 12:21PM |
R15.00008: Computing precession and spin-curvature coupling for small bodies orbiting Kerr black holes Scott Hughes, Uchupol Ruangsri, Sarah Vigeland A non-spinning small body that orbits a Kerr black hole follows a trajectory that looks like a geodesic corrected by ``self force'' effects that drive inspiral and shift the small body's orbital frequencies. If the small body is spinning, then additional forces arise from the coupling of its spin to the curvature of the larger black hole. In this talk, I will describe recent work to compute the precession of this small body in the frequency domain for generic orbit geometries and generic small body orientations, and show how this result can be used to compute the spin-curvature force in a computationally effective way. [Preview Abstract] |
Monday, April 18, 2016 12:21PM - 12:33PM |
R15.00009: Model for Quasinormal Mode Excitation by a Particle Plunging into a Black Hole Zachary Mark, Aaron Zimmerman, Huan Yang, Yanbei Chen It is known that the late time gravitational waveform produced by a particle plunging into a Kerr black hole is well described by a sum of quasinormal modes. However it is not yet understood how the early part of the waveform gives way to the quasinormal mode description, which diverges at early times, nor how the inhomogenous part of the waveform contributes. Motivated by Price, Nampalliwar, and Khanna (2015), we offer a model for quasinormal mode excitation by a particle plunging into a Schwarzschild black hole. To develop our model we study approximations to the Regge-Wheeler equation that allow for a closed-form expression for the frequency-domain Green's function, which we use to isolate the component of the waveform that should be identified with quasinormal ringing. Our description of quasinormal ringing does not diverge at early times and reveals that quasinormal ringing should be understood in analogy with a damped harmonic oscillator experiencing a transient driving source. [Preview Abstract] |
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