Quasinormal modes of black holes immersed in a strong magnetic field

TL;DR

This paper investigates the quasinormal modes of Ernst black holes immersed in strong magnetic fields, revealing that magnetic fields influence the modes' frequencies and lifetimes, with implications for black hole perturbation analysis.

Contribution

It introduces the analysis of quasinormal modes in magnetized black holes, showing how magnetic fields modify the spectrum and dynamics of perturbations.

Findings

Magnetic fields induce an effective mass in scalar perturbations.

Quasinormal modes become longer lived in magnetic fields.

Oscillation frequencies increase with magnetic field strength.

Abstract

We found quasinormal modes, both in time and frequency domains, of the Ernst black holes, that is neutral black holes immersed in an external magnetic field. The Ernst solution reduces to the Schwarzschild solution, when the magnetic field vanishes. It is found that the quasinormal spectrum for massless scalar field in the vicinity of the magnetized black holes acquires an effective "mass" $\mu = 2 B m$, where m is the azimuthal number and B is parameter describing the magnetic field. We shall show that in the presence of a magnetic field quasinormal modes are longer lived and have larger oscillation frequencies. The perturbations of higher dimensional magnetized black holes by Ortaggio and of magnetized dilaton black holes by Radu are considered.