Self-force and fluid resonances

TL;DR

This paper investigates how a perfect fluid surrounding a massive body influences the gravitational self-force on an orbiting particle, revealing resonant effects due to fluid-induced quasinormal modes, within a simplified scalar gravity model.

Contribution

It extends self-force analysis from vacuum black hole spacetimes to nonvacuum fluid environments, highlighting fluid resonances' impact on orbital dynamics.

Findings

Fluid resonances produce observable features in the self-force.

Quasinormal modes are excited during inspiral, affecting orbital evolution.

Resonant effects are demonstrated in a scalar wave model.

Abstract

The gravitational self-force acting on a particle orbiting a massive central body has thus far been computed for vacuum spacetimes involving a black hole. In this work we continue an ongoing effort to study the self-force in nonvacuum situations. We replace the black hole by a material body consisting of a perfect fluid, and determine the impact of the fluid's dynamics on the self-force and resulting orbital evolution. We show that as the particle inspirals toward the fluid body, its gravitational perturbations trigger a number of quasinormal modes of the fluid-gravity system, which produce resonant features in the conservative and dissipative components of the self-force. As a proof-of-principle, we demonstrate this phenomenon in a simplified framework in which gravity is mediated by a scalar potential satisfying a wave equation in Minkowski spacetime.