# Kerr-Newman black holes can be generically overspun

## TL;DR

This paper investigates whether Kerr-Newman black holes can be overspun through perturbations by scalar and neutrino fields, revealing conditions under which the event horizon may be destroyed, challenging aspects of the cosmic censorship conjecture.

## Contribution

It demonstrates that neutrino fields can overspin Kerr-Newman black holes regardless of backreaction effects, providing new insights into horizon stability and cosmic censorship.

## Key findings

- Scalar fields can overspin extremal black holes if backreaction is neglected.
- Neutrino fields can overspin black holes without lower frequency limits.
- Event horizon destruction by neutrino fields cannot be prevented by backreaction effects.

## Abstract

We construct thought experiments involving the perturbations of Kerr-Newman black holes by neutral test fields to evaluate the validity of the weak form of the cosmic censorship conjecture. We first show that neglecting backreaction effects, extremal Kerr-Newman black holes which satisfy the condition $(J^2/M^4)<(1/3)$ can be overspun by scalar fields. This result, which could not be discerned in the previous analyses to first order, is prone to be fixed by employing backreaction effects. However the perturbation of Kerr-Newman black holes by neutrino fields leads to a generic overspinning of the black hole due to the absence of a lower limit for the frequency of the incident wave to ensure that it is absorbed by the black hole. For this case, the destruction of the event horizon cannot be fixed by any form of backreaction effects. This result should not be interpreted as a counter-example to any of the previous results which were based on the assumption that the null energy condition is satisfied. We clarify and justify our arguments with numerical examples.