Parity violation in photon quasinormal modes of black holes

TL;DR

This paper explores how axion fields around black holes cause parity violation in photon quasinormal modes, offering a potential new way to probe dark matter and dark energy through electromagnetic signals.

Contribution

It introduces a model of black holes with axion hair, derives coupled equations for photon modes, and demonstrates parity violation in quasinormal modes using numerical methods.

Findings

Parity violation observed in photon polarization within quasinormal modes

Potential electromagnetic signatures for dark sector exploration

Numerical computation of quasinormal modes with axion coupling

Abstract

Given that black holes are ubiquitous in the universe and axion-like scalar fields are potential candidates for dark energy and/or dark matter, it is natural to consider cosmological black holes endowed with axion hair. We investigate the photon quasinormal modes of a Schwarzschild black hole with axion hair where the electromagnetic field is coupled to the axion field via a Chern-Simons interaction. We derive the master equations for the electromagnetic field as a set of coupled equations for parity-even and parity-odd modes and numerically compute quasinormal modes by using Leaver's continued fraction method. We find parity violation in the polarization of photons within the quasinormal mode spectrum. This parity violation in electromagnetic signals could serve as a new probe to explore the nature of the dark sector.