General Boosted Kerr Black Holes and Papapetrou Electrodynamics

TL;DR

This paper investigates the electromagnetic fields generated by a boosted Kerr black hole's spacetime, revealing the formation of nonsingular magnetic fields and the vanishing of electric fields under certain conditions.

Contribution

It provides a detailed analysis of Papapetrou fields in boosted Kerr spacetimes, highlighting magnetic field configurations and their dependence on boost parameters and observer frames.

Findings

Nonsingular magnetic fields form around boosted Kerr black holes.

Electric fields vanish in the analyzed configurations.

Magnetic field patterns vary with boost parameters and directions.

Abstract

In this paper the spacetime of a general boosted Kerr black hole relative to a Lorentz frame at future null infinity is regarded as a background to examine its respective Papapetrou fields. Taking into account its sole Killing vector we evaluate the electric and magnetic components -- in Bondi-Sachs (BS) and Kerr-Schild (KS) coordinates -- of the Maxwell field which comes from spacetime isometries. To this end we consider a general timelike observer in KS coordinates. Satisfying sufficient conditions for horizon and ergosphere formation it is shown that nonsingular magnetic field configurations are formed around the boosted Kerr black hole while the electric counterpart vanishes. Different magnetic field patterns are discussed in the case of variations of the boost parameter $\gamma$ and direction $\boldsymbol{\hat{n}}$.