Quasinormal mode spectrum of rotating black holes in Einstein-Gauss-Bonnet-dilaton theory

TL;DR

This paper develops a method to compute quasinormal modes of rapidly rotating black holes in Einstein-Gauss-Bonnet-dilaton theory, providing insights into their spectral properties beyond slow rotation and weak coupling regimes.

Contribution

It introduces a numerical approach to extract quasinormal modes for rotating black holes in a modified gravity theory, including exact background solutions and spectral perturbation analysis.

Findings

Spectrum matches known limits for slow rotation and weak coupling.

Deviations increase with stronger coupling.

Method enables analysis of rapidly rotating black holes in alternative gravity.

Abstract

Quasinormal modes are excited during the ringdown phase of black holes after merger. Determination of quasinormal modes of rapidly rotating black holes in alternative theories of gravity has remained a challenge for a long time. Here we discuss in detail our recently developed method to extract the quasinormal modes for rapidly rotating black holes in Einstein-Gauss-Bonnet-dilaton theory. We first obtain numerically the exact rapidly rotating background solutions, which also clarify their domain of existence. Then we solve the equations for the linear perturbations of the metric and the dilaton field by employing an appropriate set of boundary conditions and a spectral decomposition of the perturbation functions. The resulting spectrum agrees well with the known limits obtained for slow rotation and weak coupling, while it exhibits larger deviations for stronger coupling.