Unruh Effect under Non-equilibrium conditions: Oscillatory motion of an Unruh-DeWitt detector

TL;DR

This paper investigates how an Unruh-DeWitt detector responds to quantum field fluctuations during oscillatory motion, extending the understanding of the Unruh effect beyond idealized uniform acceleration conditions.

Contribution

It provides a detailed analysis of the Unruh effect under non-equilibrium, oscillatory motion, using non-equilibrium quantum field theory techniques and numerical simulations.

Findings

Late-time temperatures differ from uniform acceleration predictions

Oscillatory motion induces non-thermal detector responses

Results highlight deviations from naive Unruh effect applications

Abstract

The Unruh effect refers to the thermal fluctuations a detector experiences while undergoing linear motion with uniform acceleration in a Minkowski vacuum. This thermality can be demonstrated by tracing the vacuum state of the field over the modes beyond the accelerated detector's event horizon. However, the event horizon is well-defined only if the detector moves with eternal uniform linear acceleration. This idealized condition cannot be fulfilled in realistic situations when the motion unavoidably involves periods of non-uniform acceleration. Many experimental proposals to test the Unruh effect are of this nature. Often circular or oscillatory motion, which lacks an obvious geometric description, is considered in such proposals. The proper perspective for theoretically going beyond, or experimentally testing, the Unruh-Hawking effect in these more general conditions has to be offered by concepts and techniques in non-equilibrium quantum field theory. In this paper we provide a detailed analysis of how an Unruh-DeWitt detector undergoing oscillatory motion responds to the fluctuations of a quantum field. Numerical results for the late-time temperatures of the oscillating detector are presented. We comment on the digressions of these results from what one would obtain from a naive application of Unruh's result.