Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session G08: Analytical Methods in Gravitation |
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Sponsoring Units: DGRAV Chair: Lan-Hsuan Huang Room: Symphony III - 2nd Floor |
Sunday, April 16, 2023 10:45AM - 10:57AM |
G08.00001: The Force-Free Electromagnetic Field in Kerr Geometry: The Search for Analytic Solutions Govind Menon, Rakshak Adhikari, Mikhail V Medvedev We introduce a systematic method to find exact closed-form solutions of the force-free electromagnetic field equations in Kerr geometry. The method to look for force-free solutions in other background spacetimes will also be discussed in parallel. The search algorithm is easily adaptable to computer-aided analytical calculations using programs like Maple and Mathematica. |
Sunday, April 16, 2023 10:57AM - 11:09AM |
G08.00002: Force-Free, Electromagnetic Field in Kerr Geometry: Recent Configurations Rakshak Adhikari, Govind Menon, Mikhail V Medvedev Recent solutions to the force-free electromagnetic field configuration in Kerr geometry will be presented. We also discuss the properties, applicability, and limitations of our solutions in the study of black hole magnetospheres. |
Sunday, April 16, 2023 11:09AM - 11:21AM |
G08.00003: Approximate helical symmetry at future null infinity Aniket Khairnar, Leo C Stein Compact binary systems emit gravitational radiation that has an approximate helical symmetry at future null infinity. The symmetry is broken due to the effects of radiation reaction, precession, and eccentricity. We use the post-Newtonian formalism to find the level of failure of this symmetry due to such effects. We predict this flux analytically and compare it to the NR waveforms from SpeC simulations. In the case of low eccentrity binaries, the helical flux can be used to quantify eccentricity from waveforms. |
Sunday, April 16, 2023 11:21AM - 11:33AM |
G08.00004: Dynamics of ultrarelativistic charged particles with strong radiation reaction Yangyang Cai, Samuel E Gralla, Vasileios Paschalidis Previous studies from the astrophysics and laser physics communities have identified an interesting |
Sunday, April 16, 2023 11:33AM - 11:45AM |
G08.00005: Coordinate Invariant Limits of the Reisner-Nordstrom spacetime William Julius, Matthew Gorban, Gerald B Cleaver, Christian Brown, David McNutt Certain special limiting cases of the Reisner-Nordstrom spacetime have been of interest due to potential applications to string theoretic models. Here we review a formal limiting technique based on Cartan-Karlhede invariants and present a small extension which allows for its application to spacetimes which simultaneously are non-vacuum and non-conformally flat. We apply this technique to recover the familiar extremal limit of the Reisner-Nordstrom spacetime, as well as several other novel limits. |
Sunday, April 16, 2023 11:45AM - 11:57AM |
G08.00006: The Subclassification Problem for Stationary Axisymmetric Spacetimes Christian Brown, David McNutt, Ramesh Radhakrishnan, William Julius, Matthew Gorban, Gerald B Cleaver Four-dimensional G2 spacetimes are metrics with two abelian Killing vector fields and are of great interest of study. One method of examining such metrics is the Cartan-Karlhede (CK) algorithm which serves the purpose of classifying and comparing different spacetimes. It can be used to determine if two metrics are equivalent and thus that one can be transformed into the other via a coordinate transformation. While this method can be extremely powerful, the Cartan curvature invariants produced from each metric in the algorithm are often too complicated to compare. Equating the invariants from each may even be unsolvable. Due to this, alternative methods for comparing spacetimes have been proposed such as using differential invariants arising from the jet bundle over the spacetime in the place of curvature invariants. In this work, we outline a proposed method motivated by these alternative invariants and Papapetrou fields to define a new set of differential invariants derived from Killing vector fields that we hope will provide a simpler method of comparing spacetimes. |
Sunday, April 16, 2023 11:57AM - 12:09PM |
G08.00007: Fast eccentric and inclined inspirals into a rotating black hole Philip A Lynch, Maarten van de Meent, Vojtech Witzany, Niels Warburton Extreme mass ratio inspirals (EMRIs) are a prime gravitational wave source for the upcoming LISA mission and are expected to be both eccentric and inclined with respect to the equatorial plane of the primary. To this end, we develop a model for these inspirals using an action anlge formulaiton of the method of osculating geodesics and a toy model of the gravitational self force (GSF). The resulting equaitons of motion take hours to solve numerically for a typical EMRI. To overcome this difficulty, we employ near-identity (averaging) transformations (NITs) to remove the rapidly oscillating orbital phases from the equations of motion while accurately modelling the secular evolution of the system to the post-adiabatic accuracy required by the LISA science objectives. However, this averaging technique breaks down when the radial and polar frequencies are an integer ratio of each other and form an orbital resonace. Thus, when in the vacinity of an orbital resonance, we modify the NIT proceedure to average out all phase contributions to the equaitons of motion except those proportional to the resonant phase and when no resonance is present, we switch back to the origonal NIT proceedure. This allows us to model generic inspirals with transient resonances with post-adiabtic accuracy in a matter of seconds. |
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