Rescuing the Unruh effect in Lorentz violating gravity

Abstract

While the robustness of Hawking radiation in the presence of UV Lorentz breaking is well-established, the Unruh effect has posed a challenge, with a large literature concluding that even the low-energy restoration of Lorentz invariance may not be sufficient to sustain this phenomenon. Notably, these previous studies have primarily focused on Lorentz-breaking matter on a conventional Rindler wedge. In this work, we demonstrate that considering the complete structure of Lorentz-breaking gravity, specifically the presence of a hypersurface orthogonal æther field, leads to the selection of a new Rindler wedge configuration characterized by a uniformly accelerated æther flow. This uniform acceleration provides a reference scale for comparison with the Lorentz-breaking one, thus ensuring the persistence of the Unruh effect in this context. We establish this by calculating the expected temperature using a Bogolubov approach, and by analyzing the response of a uniformly accelerated detector. We suggest that this resilience of the Unruh effect opens interesting possibilities towards future developments for using it as a tool to constrain Lorentz breaking theories of gravity.