Generic features of Einstein-Aether black holes

TL;DR

This paper explores spherically symmetric black hole solutions in Einstein-Aether theory, allowing superluminal modes and analyzing their properties, which differ from Schwarzschild black holes in key physical aspects.

Contribution

It introduces black hole solutions with superluminal spin-0 modes and a spin-0 horizon inside the event horizon, expanding understanding of Einstein-Aether black holes.

Findings

Black holes can have a spin-0 horizon inside the event horizon.

Significant differences from Schwarzschild black holes in mass, orbit, and temperature.

Superluminal propagation affects black hole structure and properties.

Abstract

We reconsider spherically symmetric black hole solutions in Einstein-Aether theory with the condition that this theory has identical PPN parameters as those for general relativity, which is the main difference from the previous research. In contrast with previous study, we allow superluminal propagation of a spin-0 Aether-gravity wave mode. As a result, we obtain black holes having a spin-0 "horizon" inside an event horizon. We allow a singularity at a spin-0 "horizon" since it is concealed by the event horizon. If we allow such a configuration, the kinetic term of the Aether field can be large enough for black holes to be significantly different from Schwarzschild black holes with respect to ADM mass, innermost stable circular orbit, Hawking temperature, and so on. We also discuss whether or not the above features can be seen in more generic vector-tensor theories.