Destroying a near-extremal Kerr-Newman black hole

TL;DR

This paper extends Wald's analysis to near-extremal Kerr-Newman black holes, demonstrating that their event horizons can be destroyed by test particles, potentially creating naked singularities, and identifies optimal parameters for such destruction.

Contribution

It provides a detailed analysis of how near-extremal Kerr-Newman black holes can be turned into naked singularities by test particles, including optimal charge and angular momentum values.

Findings

Near-extremal black holes can be destroyed by test particles.

Optimal parameters for particle charge and angular momentum are identified.

Potential astrophysical scenarios for naked singularity formation are discussed.

Abstract

We revisit here a previous argument due to Wald showing the impossibility of turning an extremal Kerr-Newman black hole into a naked singularity by plunging test particles across the black hole event horizon. We extend Wald's analysis to the case of near-extremal black holes and show that it is indeed possible to destroy their event horizon, giving rise to naked singularities, by pushing test particles towards the black hole as, in fact, it has been demonstrated explicitly by several recent works. Our analysis allows us to go a step further and to determine the optimal values, in the sense of keeping to a minimum the backreaction effects, of the test particle electrical charge and angular momentum necessary to destroy a given near-extremal Kerr-Newman black hole. We describe briefly a possible realistic scenario for the creation of a Kerr naked singularity from some recently discovered candidates to be rapidly rotating black holes in radio galaxies.