Quasinormal modes, scattering and Hawking radiation of Kerr-Newman black holes in a magnetic field

TL;DR

This paper investigates how a magnetic field influences the oscillations, scattering, and Hawking radiation of Kerr-Newman black holes, revealing that magnetic fields accelerate black hole evaporation and slightly alter quasinormal modes.

Contribution

It provides a detailed analysis of the effects of magnetic fields on black hole radiation and oscillations, highlighting the impact of Zeeman shift and Faraday induction in this context.

Findings

Magnetic fields increase energy-emission rates from black holes.

Black holes in magnetic fields evaporate faster and reach extremality sooner.

Quasinormal modes are only moderately affected by magnetic fields.

Abstract

We perform a comprehensive analysis of the spectrum of proper oscillations (quasinormal modes), transmission/reflection coefficients and Hawking radiation for a massive charged scalar field in the background of the Kerr-Newman black hole immersed in an asymptotically homogeneous magnetic field. There are two main effects: the Zeeman shift of the particle energy in the magnetic field and the difference of values of an electromagnetic potential between the horizon and infinity, i.e. the Faraday induction. We have shown that "turning on" the magnetic field induces a stronger energy-emission rate and leads to "recharging" of the black hole. Thus, a black hole immersed in a magnetic field evaporates much quicker, achieving thereby an extremal state in a shorter period of time. Quasinormal modes are moderately affected by the presence of a magnetic field which is assumed to be relatively small compared to the gravitational field of the black hole.