Black holes in degenerate Einstein Gauss-Bonnet gravity: Can QNMs distinguish them from GR?

TL;DR

This paper investigates the quasinormal modes of black holes in degenerate Einstein Gauss-Bonnet gravity, comparing their ringdown signatures with those in General Relativity to assess distinguishability.

Contribution

It provides the first analysis of black hole QNMs in degenerate Einstein Gauss-Bonnet gravity, including stability and comparison with GR solutions.

Findings

Black holes exist for specific Gauss-Bonnet coupling ranges.

Both branches of solutions are asymptotically well-defined.

QNMs differ from GR, potentially allowing observational distinction.

Abstract

In this study, for the first time, we analyse the quasinormal modes of black holes occurring within the framework of degenerate gravity. We investigate the properties of the asymptotically flat spacetimes introduced recently in [JCAP 02(2022)02] that satisfy degenerate Einstein Gauss-Bonnet(dEGB) action and belong to a much larger class of solutions which include cosmological constant. This solution has two distinct branches akin to Einstein Gauss-Bonnet(EBG) gravity. However, unlike the EBG solutions, both the branches of dEGB are well-defined asymptotically. The negative branches from both theories can be identified for the asymptotically flat case. We observe black holes for specific ranges of the Gauss-Bonnet coupling parameter and perform a stability analysis by calculating the quasinormal modes (QNMs) under scalar wave propagation. Finally, the ringdown spectrums of our black holes are compared with their GR counterparts.