Quasinormal modes of spontaneous scalarized Kerr black holes

TL;DR

This paper calculates the quasinormal modes of scalarized Kerr black holes in Einstein-scalar-Gauss-Bonnet gravity, revealing mode splitting that could help test alternative gravity theories through gravitational wave observations.

Contribution

First nonperturbative calculation of QNMs for scalarized Kerr black holes without assuming small spin or weak coupling, showing mode splitting and potential observational signatures.

Findings

Universal splitting of fundamental mode into multiple branches

Breaking of isospectrality in scalarized black holes

Potential to test beyond-GR physics with gravitational wave data

Abstract

Recent studies have shown that rotating black holes can undergo spontaneous scalarization, leading to deviations from general relativity in the strong-field regime. We present the first nonperturbative calculation of the quasinormal modes (QNMs) of scalarized Kerr black holes in Einstein-scalar-Gauss-Bonnet gravity, without assuming small spin or weak coupling. Our results reveal a universal splitting of the fundamental $l=m=2$ mode into axial-led, polar-led, and scalar-led branches, breaking the isospectrality characteristic of Kerr black holes. This splitting offers distinct signatures in the ringdown phase of gravitational wave signals and provides a new avenue to test gravity in the strong-field regime. Our findings open the possibility of probing beyond-GR physics using precision measurements of black hole ringdowns in upcoming gravitational wave observations.