Charging up Boosted Black Holes

TL;DR

This paper proposes that boosted black holes can acquire and maintain charge in magnetic fields, leading to unique electromagnetic signatures that could be observable, challenging previous assumptions about black hole discharge.

Contribution

It introduces the idea that boosted black holes can preferentially charge through gravito-electrodynamics, producing observable electromagnetic signatures.

Findings

Black holes can charge preferentially when boosted in magnetic fields.

Charged test particles exhibit chaotic, fractal basin boundaries.

Boosted black holes generate their own electromagnetic fields and luminosity.

Abstract

Contrary to a prevailing assumption that black holes would swiftly discharge, we argue that black holes can charge preferentially when boosted through an ambient magnetic field. Though the details are very different, the preference for charge is related to the precipitation of the Wald charge on a spinning black hole in an ambient magnetic field. The gravito-electrodynamics upstage naive arguments about screening electric fields in determining the value of the charge accrued. Charged test particles, which build up the black hole charge, exhibit chaotic behavior as evidenced by fractal basin boundaries between dynamical regions. Charged, boosted black holes will generate their own electromagnetic fields and thereby their own luminous signatures, even if they are initially bare. We therefore add boosted black holes to the growing list of potentially observable black hole signatures, alongside black hole batteries and black hole pulsars. The implications should be relevant for supermassive black holes that are boosted relative to a galactic magnetic field as well as black holes merging with magnetized neutron stars.