The Unruh effect without thermality

TL;DR

This paper demonstrates that accelerated detectors can exhibit thermal features characteristic of the Unruh effect even without satisfying the KMS condition, challenging the traditional understanding of the effect's prerequisites.

Contribution

It establishes that the KMS condition is sufficient but not necessary for the Unruh effect, providing new criteria for thermal response in accelerated detectors.

Findings

Accelerated detectors can show thermal features without KMS satisfaction.

Thermal detailed balance and Planckian response can occur independently of the KMS condition.

Necessary and sufficient conditions for thermal response in the adiabatic limit are identified.

Abstract

We show that uniformly accelerated detectors can display genuinely thermal features even if the Kubo-Martin-Schwinger (KMS) condition fails to hold. These features include satisfying thermal detailed balance and having a Planckian response identical to cases in which the KMS condition is satisfied. In this context, we discuss that satisfying the KMS condition for accelerated trajectories is just sufficient but not necessary for the Unruh effect to be present in a given quantum field theory. Furthermore, we extract the necessary and sufficient conditions for the response function of an accelerated detector to be thermal in the infinitely adiabatic limit. This analysis provides new insights about the interplay between the KMS condition and the Unruh effect, and a solid framework in which the robustness of the Unruh effect against deformations of quantum field theories (perhaps Lorentz-violating) can be answered unambiguously.