Limits on the mass of compact objects in Ho\v{r}ava-Lifshitz gravity

TL;DR

This paper investigates theoretical mass limits for compact objects within Hořava-Lifshitz gravity, revealing how these limits relate to black hole extremality and horizon properties, similar to known limits in general relativity.

Contribution

It derives and analyzes the mass limits for compact objects in Hořava-Lifshitz gravity, extending classical limits to this modified gravity framework.

Findings

Uniform density limit and sound speed limit curves meet the horizon curve at the extremal black hole point.

Both limits converge at the minimum of the horizon, where black holes become extremal.

The results connect mass limits with black hole extremality in HL gravity.

Abstract

It is known that there exist theoretical limits on the mass of compact objects in general relativity. One is the Buchdahl limit for an object with an arbitrary equation-of-state that turns out to be the limit for an object with uniform density. Another one is the causal limit that is stronger than the Buchdahl limit and is related to the speed of sound inside an object. Similar theoretical limits on the mass of compact objects in deformed Ho\v{r}ava-Lifshitz (HL) gravity are found in this \paper. Interestingly, the both curves of the uniform density limit and the sound speed limit meet the horizon curve at the minimum of the horizon, where a black hole becomes extremal, i.e., $M=q$, considering the Kehagias-Sfetsos vacuum that is an asymptotic flat solution in the HL gravity.