Why does the Unruh effect rely on Lorentz invariance, while Hawking radiation does not ?

TL;DR

This paper demonstrates that the Unruh effect fundamentally depends on Lorentz invariance, unlike Hawking radiation, which can persist without it, highlighting key differences in their theoretical foundations.

Contribution

The study reveals that Lorentz invariance is essential for the Unruh effect, contrasting with the robustness of Hawking radiation under Lorentz symmetry breaking.

Findings

Unruh effect disappears without Lorentz invariance

Hawking radiation remains under certain Lorentz symmetry violations

Discrepancy explained by different underlying mechanisms

Abstract

We show that without Lorentz invariance, the Unruh effect does not exist. We use modified dispersion relations and describe in turn: the non-thermal nature of the vacuum (defined in the preferred frame) restricted to the Rindler wedge, the loss of the KMS property of the Wigthman function, the transition amplitudes and transition rates of a uniformaly accelerated detector. This situation seems to contrast with the Hawking radiation of acoustic black holes, which under certain assumptions has been shown to be robust to a breaking of Lorentz symmetry. We explain this discrepancy.