Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session Y7: Gravitational Self-Force and Orbits |
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Sponsoring Units: GGR Chair: Eanna Flanagan, Cornell University Room: Key 3 |
Tuesday, April 14, 2015 1:30PM - 1:42PM |
Y7.00001: The Eikonal Quasinormal Modes of Kerr-Newman Black Holes Zachary Mark, Huan Yang, Aaron Zimmerman, Yanbei Chen Due to the complicated coupling between gravity and electromagnetism near a Kerr-Newman black hole, a master, separable equation governing gravitational or electromagnetic perturbations has yet to be discovered, impeding efforts to calculate the quasinormal modes of perturbed black holes with arbitrary spin and charge. Instead, gravitational and electromagnetic perturbations are found to obey a pair of coupled, partial differential equations. To study the quasinormal modes, we examine these equations in the eikonal limit (where the waves are rapidly changing in space and time) via a newly developed WKB technique capable of handling coupled wave equations. Surprisingly, it turns out that an approximate master equation introduced by Dudley and Finley provides an accurate description of perturbations in the eikonal regime. These techniques allow the ``geometric correspondence'' between quasinormal modes and photon geodesics that is known to be true for Kerr black holes to be extended to Kerr-Newman black holes. [Preview Abstract] |
Tuesday, April 14, 2015 1:42PM - 1:54PM |
Y7.00002: Gravitational radiation during plunge - a Green's function approach Sourabh Nampalliwar, Richard Price, Gaurav Khanna During the merger of binary compact objects, an important stage is the plunge. A short part of the Gravitational waveform, it marks the end of early inspiral and determines the quasinormal ringing (QNR) of the final product of the merger. In this talk, we describe the approach of using the Fourier domain Green's function in the particle perturbation approximation to understand the excitation of QNR. We show that the resulting understanding is successful in explaining QNR in toy models and in the Schwarzschild background. [Preview Abstract] |
Tuesday, April 14, 2015 1:54PM - 2:06PM |
Y7.00003: Static Self-Forces in Five Dimensions Peter Taylor There has been considerable recent interest in the self-force formalism in higher dimensional space-times, particularly in odd dimensions since the analogue of the Detweiler-Whiting singular field is unknown. Moreover, a recent article by Beach, Poisson and Nickel provocatively suggests that the self-force in five dimensions depends on the internal structure of the charge. In this talk, I will develop an axiomatic approach to construct a singular field for a static point particle in 5D. I will then revisit the calculation of the self-force on a static charge in a 5D black hole space-time and show that, in the context of our regularization prescription, the self-force does not depend on the internal structure. [Preview Abstract] |
Tuesday, April 14, 2015 2:06PM - 2:18PM |
Y7.00004: Applying the effective-source approach to gravitational self-force calculations Barry Wardell The equations of motion of a point particle interacting with its own field are defined in terms of a certain regularized self-field. A leading method for computing this regularized field is the effective-source approach, which has the benefit of being applicable in cases where traditional mode-sum regularization is inadequate. This approach has previously been successfully applied in scalar-field toy models and in a restricted class of gravitational-field models. In this talk I will present recent progress on gravitational effective-source calculations, with a particular focus on applications at second perturbative order. [Preview Abstract] |
Tuesday, April 14, 2015 2:18PM - 2:30PM |
Y7.00005: Radiation-Reaction Force on a Small Charged Body to Second Order Jordan Moxon, Eanna Flanagan In classical electrodynamics, an accelerating charge emits radiation and experiences a corresponding radiation reaction force, or self force. We extend to greater precision (higher order in perturbation theory) a previous rigorous derivation of the electromagnetic self force in flat spacetime by Gralla, Harte, and Wald. The method introduced by Gralla, Harte, and Wald computes the self-force from the Maxwell field equations and conservation of stress-energy, and does not require regularization of a singular point charge, as has been necessary in prior computations. For our higher order compuation, it becomes necessary to adopt an adjusted definition of the mass of the body to avoid including self-energy from the electromagnetic field sourced during the history of the body. We derive the evolution equations for the mass, spin, and center of mass position of an extended body through second order using our adjusted formalism. The final equations give an acceleration dependent evolution of the spin (self-torque), as well as a mixing between the extended body effects and the acceleration dependent effects on the overall body motion. [Preview Abstract] |
Tuesday, April 14, 2015 2:30PM - 2:42PM |
Y7.00006: Particle on the Innermost Stable Circular Orbit of a Rapidly Spinning Black Hole Samuel Gralla, Achilleas Porfyriadis We consider the field of a particle orbiting on the innermost stable circular orbit of a nearly extremal Kerr black hole. We derive an analytic expression for the scaling of the power radiated as extremality is approached. This can be viewed as a ``critical exponent'' for the simplified behavior near the zero-temperature point of the Kerr family. [Preview Abstract] |
Tuesday, April 14, 2015 2:42PM - 2:54PM |
Y7.00007: Self-force on Accelerated Particles in Schwarzschild Thomas Linz, Eric Van Oeveren, Alan Wiseman In this work we extend the techniques of Hikida et. al. (2005) and calculate the scalar self-force on particles moving along accelerated circular orbits in Schwarzschild. By reformulating the earlier analytic methods for solving the Teukolsky equation (Mano, Suzuki, and Takasugi, 1996), Hikida demonstrated some useful features of the solutions which simplify self-force calculations, and then utilized these techniques to produce a low frequency expansion of the scalar self-force on a particle undergoing geodesic, circular motion in Schwarzschild spacetime. We further expand on these techniques by allowing the particle to move along circular orbits with an arbitrary orbital frequency. By relaxing the restriction to geodesic motion, we are able to both compare the results with a wider range of simpler examples and distinguish the effects on the self-force from the background curvature of the spacetime and from the particle's motion. These methods may lead to further insights regarding the self-force regularization. [Preview Abstract] |
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