Scattering of particles by deformed non-rotating black holes

TL;DR

This paper investigates how gravitational waves emitted by particles scattering off deformed black holes can reveal deviations from the standard Schwarzschild solution, enabling tests of alternative gravity models.

Contribution

It introduces an effective deformation parameter to quantify deviations from Schwarzschild black holes and demonstrates how gravitational wave measurements can constrain these deviations.

Findings

Deviations from Schwarzschild can be detected via gravitational wave spectra.

The effective deformation parameter captures metric deviations.

Gravitational wave signals can test black hole geometry.

Abstract

We study the excitation of axial quasi-normal modes of deformed non-rotating black holes by test-particles and we compare the associated gravitational wave signal with that expected in general relativity from a Schwarzschild black hole. Deviations from standard predictions are quantified by an effective deformation parameter, which takes into account deviations from both the Schwarzschild metric and the Einstein equations. We show that, at least in the case of non-rotating black holes, it is possible to test the metric around the compact object, in the sense that the measurement of the gravitational wave spectrum can constrain possible deviations from the Schwarzschild solution.