Unruh effect without Rindler horizon

TL;DR

This paper explores the Unruh effect in a 2D Minkowski space with a perfect mirror that blocks the Rindler horizon, revealing that thermodynamic properties persist but the particle distribution can be non-thermal depending on initial conditions.

Contribution

It demonstrates that the Unruh effect's thermodynamic features remain even when the Rindler horizon is masked, and analyzes the impact of initial conditions on the thermal nature of Rindler particle distribution.

Findings

Thermodynamic properties of the Unruh effect are unchanged despite horizon masking.

The Rindler particle distribution can be non-thermal with certain initial conditions.

An effective thermal behavior emerges when restricting to finite norm Rindler states.

Abstract

We investigate the Unruh effect for a massless scalar field in the two dimensional Minkowski space in the presence of a uniformly accelerated perfect mirror, with the trajectory of the mirror chosen in such a way that the mirror completely masks the Rindler horizon from the space-time region of interest. We find that the characteristic thermodynamical properties of the effect remain unchanged, i.e. the response of a uniformly co-accelerated Unruh detector and the distribution of the Rindler particles retain their thermal form. However, since in this setup there are no unobserved degrees of freedom of the field the thermal statistics of the Rindler particles is inconsistent with an initial pure vacuum, which leads us to reconsider the problem for the more physical case when the mirror is inertial in the past. In these conditions we find that the distribution of the Rindler particles is non-thermal even in the limit of infinite acceleration times, but an effective thermal statistics can be recovered provided that one restricts to the expectation values of smeared operators associated to finite norm Rindler states. We explain how the thermal statistics in our problem can be understood in analogy with that in the conventional version of the effect.