Asymptotic states of accelerated detectors and universality of the Unruh effect

TL;DR

This paper investigates how uniformly accelerated detectors perceive quantum fields, showing that while early responses depend on interaction details, the long-term state is universally thermal at the Unruh temperature.

Contribution

It demonstrates that regardless of interaction type, the late-time state of an accelerated detector is always thermal, highlighting the universality of the Unruh effect.

Findings

Early-time transition rate varies with interaction type.

Late-time state is always thermal at Unruh temperature.

Universality of the Unruh effect in asymptotic states.

Abstract

We treat an Unruh-DeWitt detector as an open quantum system and evaluate the response of a uniformly accelerated detector: (i) interacting locally with the derivatives of a massless scalar field and (ii) linearly coupled to an electromagnetic field. We find that the early-time transition rate of the detector strongly depends on the type of the interaction between the detector and the quantum field, and may not follow a Planck distribution. In contrast, the late time asymptotic state is always thermal at the Unruh temperature and thus provides a more fundamental and persistent characterization of the acceleration temperature: A uniformly accelerated detector experiences the field vacuum as a genuine thermal bath at the Unruh temperature and eventually settles at a thermal state, regardless of their intermediate dynamics or the type of interaction.