Unruh-DeWitt Detector Differentiation of Black Holes and Exotic Compact Objects

TL;DR

This paper investigates how a static Unruh-DeWitt detector can distinguish between black holes and exotic compact objects (ECOs) by analyzing their different response rates, revealing potential observational signatures.

Contribution

It introduces a detailed analysis of the detector's response to ECOs with various boundary conditions, highlighting differences from black holes and identifying resonance effects.

Findings

Response rate differs significantly between black holes and ECOs.

Resonance structures depend on ECO boundary location and reflectivity.

Analysis connects response features to ECO vacuum modes and transfer functions.

Abstract

We study the response of a static Unruh-DeWitt detector outside an exotic compact object (ECO) with a general reflective boundary condition in 3+1 dimensions. The horizonless ECO, whose boundary is extremely close to the would-be event horizon, acts as a black hole mimicker. We find that the response rate is notably distinct from the black hole case, even when the ECO boundary is perfectly absorbing. For a (partially) reflective ECO boundary, we find resonance structures in the response rate that depend on the different locations of the ECO boundary and those of the detector. We provide a detailed analysis in connection with the ECO's vacuum mode structure and transfer function.