Quasi-normal modes of spherically symmetric black hole spacetimes with cosmic string in a Dirac field

TL;DR

This paper derives the Dirac equation for black holes with cosmic strings and computes their quasi-normal mode frequencies, revealing that cosmic strings reduce decay rates in various black hole spacetimes.

Contribution

It introduces a general Dirac equation for black holes with cosmic strings and calculates quasi-normal modes for multiple black hole types using WKB approximation.

Findings

Decay rates are lower in black holes with cosmic strings.

Quasi-normal mode frequencies vary with the presence of cosmic strings.

Cosmic strings influence the stability properties of black hole spacetimes.

Abstract

Dirac equation for a general black hole metric having a cosmic string is derived. The quasi-normal mode frequencies for Schwarzschild, RN extremal, SdS and near extremal SdS black hole space-times with cosmic string perturbed by a massless Dirac field are obtained using WKB approximation and found that in all these cases, decay is less in black holes having cosmic string compared to black holes with out string.