Self-Consistent Evolution of Extreme Mass Ratio Inspirals

Louisiana State University, Baton Rouge LA

Investigators

Abstract

We will investigate extreme-mass-ratio inspirals (EMRIs) of compact objects in orbit around super-massive black holes that, due to emission of gravitational waves, eventually plunge into the super-massive black hole. We will generalize existing methods based on the effective source approach from the scalar case to the more interesting (and demanding) gravitational case with the aim of being able to perform fully self-consistent evolutions of both the particle trajectory and the radiation field. EMRIs are expected to be a major source of gravitational waves for future space-based gravitational wave detectors. The observation of such events can be used to test the black hole No-Hair Theorem by mapping out the black hole metric as the small compact object spirals in. However, a successful test will require very accurate predictions of the full gravitational waveform with small phase errors over hundreds of thousands to millions of orbital periods. The slow orbital evolution is determined by the interaction of the particle with the perturbations produced by the particle itself, the so called self-force. Though the radiative part of the self-force is solely responsible for the evolution of the orbital parameters resulting in amplitude and frequency evolution of the waveform, the conservative piece can still affect the phase. Current approaches to calculating EMRI waveforms evolve the system as if it were going from one geodesic to the next. The change of the orbital parameters is calculated from averages of fluxes or the self-force itself over several orbits. The approximate methods have to be checked with fully self-consistent evolutions of both the orbit and gravitational perturbations. Using the effective source approach, such self-consistent evolutions are now within reach. This project will leverage and integrate with several complementary NSF projects which focus on developing open-source codes and building research communities across many fields of science. Within these communities, this project will broaden the existing infrastructure and computational methods and make them available not only to our group but to the broader self-force community. A central part of this proposal is the training of a graduate student. The student will be integrated into both the numerical relativity group at LSU and the international self-force community. PI Diener participates in two REU programs at LSU (one at the CCT, one in the physics department) where undergraduates gain research experience in computational relativistic astrophysics using real production code via simple user interfaces developed in the Cactus group at the CCT. In the coming years the REU research projects will be based on this project.