Destroying extremal Kerr-Newman black holes with test particles

TL;DR

This paper demonstrates that extremal Kerr-Newman black holes can be destroyed by test particles, potentially violating cosmic censorship, but radiative and self-force effects might prevent such violations in realistic scenarios.

Contribution

It explicitly shows that higher order effects allow destruction of extremal black holes, challenging previous assumptions about cosmic censorship.

Findings

Extremal Kerr-Newman black holes can be destroyed by test particles.

The parameter range for particle destruction is very narrow.

Radiative and self-force effects may prevent violations in realistic cases.

Abstract

It has been shown that a nearly extremal black hole can be overcharged or overspun by a test particle if radiative and self-force effects are neglected, indicating that the cosmic censorship might fail. In contrast, the existing evidence in literature suggests that an extremal black hole cannot be overcharged or overspun in a similar process. In this paper, we show explicitly that even an exactly extremal black hole can be destroyed by a test particle, leading to a possible violation of the cosmic censorship. By considering higher order terms, which were neglected in previous analysis, we show that the violation is generic for any extremal Kerr-Newman black hole with nonvanishing charge and angular momentum. We also find that the allowed parameter range for the particle is very narrow, indicating that radiative and self-force effects should be considered and may prevent violation of the cosmic censorship.