Cosmic Censorship: As Strong As Ever

TL;DR

This paper demonstrates the classical instability of Cauchy horizons inside charged black holes in de Sitter spacetime, reaffirming the robustness of strong cosmic censorship against certain counter-examples.

Contribution

It shows that all previously considered counter-examples to strong cosmic censorship are unstable due to outgoing modes near the event horizon, reinforcing the conjecture's validity.

Findings

Cauchy horizons are classically unstable in charged black holes with de Sitter backgrounds.

Outgoing modes near the event horizon drive the instability.

The mechanism applies to other proposed counter-examples of strong cosmic censorship.

Abstract

Spacetimes which have been considered counter-examples to strong cosmic censorship are revisited. We demonstrate the classical instability of the Cauchy horizon inside charged black holes embedded in de Sitter spacetime for all values of the physical parameters. The relevant modes which maintain the instability, in the regime which was previously considered stable, originate as outgoing modes near to the black hole event horizon. This same mechanism is also relevant for the instability of Cauchy horizons in other proposed counter-examples of strong cosmic censorship.