What happens once an accelerating observer has detected a Rindler particle?

TL;DR

This paper explores the implications of measuring Rindler particles on the possibility of superluminal communication, analyzing the non-local effects and potential physical constraints that prevent faster-than-light signaling.

Contribution

It revisits the Unruh-Wald framework to examine the effects of particle measurement on field states and the implications for superluminal communication in semiclassical gravity.

Findings

Measurement induces non-local changes in the field state.

Potential for superluminal signaling exists theoretically.

Physical principles may prevent faster-than-light communication.

Abstract

In a seminal paper, Unruh and Wald found that the detection of a right Rindler particle by a linearly uniformly accelerated detector coupled to a Klein-Gordon field in the Minkowski vacuum leads to the creation of a Minkowski particle from the inertial viewpoint. In this paper, we revisit the framework studied by Unruh and Wald, but now consider in addition what happens once the particle has been measured somewhere in the right Rindler wedge. From an orthodox point of view, the change in the field state induced by the measurement is non-local and occurs both in the left and right Rindler wedges. If one takes semiclassical gravity seriously in this context, this seems to open the possiblity for designing superluminal communication protocols between two spacelike separated observers confined to the right and left Rindler wedges respectively. We discuss the possible ways in which physics could prevent such measurement-induced, faster-than-light signaling protocols.