The equivalence principle and QFT: Can a particle detector tell if we live inside a hollow shell?

TL;DR

This paper demonstrates that a particle detector can detect non-local spacetime structures, such as a hollow shell, within times much shorter than the light-crossing time, revealing non-local information beyond local metric indistinguishability.

Contribution

It shows that particle detectors can distinguish non-local spacetime features in short timescales, challenging the assumption that local measurements only reveal local geometry.

Findings

Particle detectors can differentiate hollow shells from flat space within short switching times.

Local metric indistinguishability does not imply inability to detect non-local structures.

Non-local spacetime features influence detector responses even at scales much shorter than the characteristic non-locality.

Abstract

We show that a particle detector can distinguish the interior of a hollow shell from flat space for switching times much shorter than the light-crossing time of the shell, even though the local metrics are indistinguishable. This shows that a particle detector can read out information about the non-local structure of spacetime even when switched on for scales much shorter than the characteristic scale of the non-locality.