Scalar quasinormal modes of rotating black holes in parity-violating gravity

TL;DR

This paper investigates how parity-violating modifications to rotating black holes affect scalar quasinormal modes, revealing potential observational signatures for new physics in strong gravity regimes.

Contribution

It provides a perturbative analysis of scalar QNMs on a conformal Kerr background with parity violation, covering the full spin range from non-rotating to near-extremal.

Findings

Parity-violating effects cause measurable shifts in QNM frequencies.

Deviations from Kerr QNMs are significant at high spins.

Results suggest QNMs as probes of parity-violating gravity theories.

Abstract

Recently, an exact rotating black hole solution in a parity-violating theory of gravity was obtained via a conformal transformation of the Kerr solution in general relativity, with parity-violating effects encoded in the conformal factor. We study the quasinormal modes (QNMs) of a test scalar field minimally coupled to gravity on this conformal Kerr background, treating the parity-violating effects perturbatively while allowing for arbitrary black hole spin, from the non-rotating case to the near-extremal regime. For low spin, we derive a perturbative formula for the QNM frequencies that includes the leading-order parity-violating correction. For high spin, particularly in the near-extremal regime, we find sizable deviations from the Kerr QNM frequencies. Our results point to a new avenue for probing parity-violating physics in the strong-gravity regime through black hole QNMs.