Ringing out General Relativity: Quasi-normal mode frequencies for black holes of any spin in modified gravity

TL;DR

This paper introduces a general perturbative spectral method to compute quasinormal mode frequencies of black holes with any spin in modified gravity theories, aiding gravitational wave tests of gravity.

Contribution

It develops a versatile method for calculating black hole quasinormal modes in various modified gravity theories, applicable to any subextremal spin.

Findings

Method accurately computes quasinormal modes in scalar-Gauss-Bonnet gravity.

Enables robust tests of gravity using gravitational wave ringdown data.

Applicable to black holes with any subextremal spin.

Abstract

After black holes collide, the remnant settles to a stationary state by emitting gravitational waves. Once non-linearities subside, these ringdown waves are dominated by exponentially-damped sinusoids, or quasinormal modes. We develop a general method using perturbative spectral expansions to calculate the quasinormal-mode frequencies and damping times in a wide class of modified gravity theories for black holes with any subextremal spin. We apply this method to scalar-Gauss-Bonnet gravity to show its accuracy, thus enabling robust ringdown tests with gravitational wave data.