Cosmic Censorship in Lorentz Violating Theories of Gravity

TL;DR

This paper investigates the robustness of Cosmic Censorship in Lorentz violating gravity theories, showing that universal horizons prevent singularities from being observable, even in complex spinning black hole spacetimes.

Contribution

It extends previous results to 3+1d dynamical and spinning spacetimes, demonstrating the formation of universal horizons that uphold a form of Cosmic Censorship in Einstein-Aether theories.

Findings

Universal horizons form between outer and inner horizons in spinning black holes.

Geometry never evolves beyond the universal horizon, preventing exposure of singularities.

Multiple stationary universal horizons exist for spinning black holes, with only one matching spherical solutions.

Abstract

Is Cosmic Censorship special to General Relativity, or can it survive a violation of equivalence principle? Recent studies have shown that singularities in Lorentz violating Einstein-Aether (or Horava-Lifhsitz) theories can lie behind a universal horizon in simple black hole spacetimes. Even infinitely fast signals cannot escape these universal horizons. We extend this result, for an incompressible aether, to 3+1d dynamical or spinning spacetimes which possess inner killing horizons, and show that a universal horizon always forms in between the outer and (would-be) inner horizons. This finding suggests a notion of Cosmic Censorship, given that geometry in these theories never evolves beyond the universal horizon (avoiding potentially singular inner killing horizons). A surprising result is that there are 3 distinct possible stationary universal horizons for a spinning black hole, only one of which matches the dynamical spherical solution. This motivates dynamical studies of collapse in Einstein-Aether theories beyond spherical symmetry, which may reveal instabilities around the spherical solution.