Nature of Singularities in Vector-Tensor Theories of Gravity

TL;DR

This paper explores how singularities and horizons in Vector-Tensor theories of gravity differ from those in General Relativity, highlighting unique features like naked singularities and new cosmological singularities.

Contribution

It demonstrates that Vector-Tensor theories exhibit fundamentally different singularity structures compared to GR, using Einstein-aether theory as a case study.

Findings

Vacuum black hole solutions have naked singularities.

Vacuum cosmological solutions exhibit new singularities absent in GR.

Deviations could be explored through gravitational wave observations.

Abstract

The Vector-Tensor (VT) theories of gravity are a class of alternative theories to General Relativity (GR) that are characterized by the presence of a dynamical vector field besides the metric. They are studied in attempts to understand spontaneous Lorentz violation, to generate massive gravitons, and as models of dark matter and dark energy. In this article, I outline how the nature of singularities and horizons in VT theories differ greatly from GR even under the same ordinary conditions. This is illustrated with Einsteinaether theory where vacuum black hole solutions have naked singularities and vacuum cosmological solutions have new singularities that are otherwise absent in GR. It would be interesting to explore these deviations using gravitational waves