Hawking Radiation from Universal Horizons

TL;DR

This paper demonstrates that Hawking radiation from universal horizons in Lorentz breaking gravity theories is consistent with thermodynamic laws, using two complementary derivations that confirm the temperature is determined by the surface gravity.

Contribution

It provides the first consistent derivation of Hawking radiation from universal horizons, confirming the thermodynamic behavior in Lorentz breaking gravity theories.

Findings

Hawking temperature is set by the universal horizon surface gravity.

Both derivations agree on the temperature being consistent with thermodynamics.

Results support the survival of black hole thermodynamics in Lorentz breaking theories.

Abstract

The persistence of a suitable notion of black hole thermodynamics in Lorentz breaking theories of gravity is not only a non-trivial consistency test for such theories, it is also an interesting investigation {\em per se}, as it might help us identifying the crucial features at the root of these surprising laws governing such purely gravitational objects. In past investigations, controversial findings were presented in this sense. With the aim of settling this issue, we present here two complementary derivations of Hawking radiation in geometries endowed with universal horizons: a novel feature of back holes in Lorentz breaking theories of gravity which reproduces several properties normally characterizing Killing horizons. We find that both the derivations agree on the fact that the Hawking temperature associated to these geometries is set by the generalized universal horizon peeling surface gravity, as required for consistency with extant derivations of the first law of thermodynamics for these black holes. We shall also comment on the compatibility of our results with previous alternative derivations and on their significance for the survival of the generalized second law of black hole thermodynamics in Lorentz breaking theories of gravity.