Quantum correlations across the horizon in acoustic and gravitational Black Holes

TL;DR

This paper compares quantum correlations across horizons in acoustic and gravitational black holes, revealing differences in correlation signatures due to the presence of a quantum atmosphere and singularity effects.

Contribution

It demonstrates the contrasting correlation patterns in acoustic versus gravitational black holes, highlighting the role of the quantum atmosphere and singularity in Hawking radiation.

Findings

Correlation peaks appear only at unequal times in gravitational black holes.

Acoustic black holes show correlation peaks along particle trajectories at equal times.

The quantum atmosphere influences the origin and detection of Hawking radiation.

Abstract

We investigate, within the framework of Quantum Field Theory in curved space, the correlations across the horizon of a black hole in order to highlight the particle-partner pair creation mechanism at the origin of Hawking radiation. The analysis concerns both acoustic black holes, formed by Bose-Einstein condensates, and gravitational black holes. More precisely, we have considered a typical acoustic black hole metric with two asymptotic homogeneous regions and the Schwarzschild metric as describing a gravitational black hole. By considering equal time correlation functions, we find a striking disagreement between the two cases: the expected characteristic peak centered along the trajectories of the Hawking particles and their partners seems to appear only for the acoustic black hole and not for the gravitational Schwarzschild one. The reason for that is the existence of a 'quantum atmosphere' displaced from the horizon as the locus of origin of Hawking radiation together, and this is the crucial aspect, with the presence of a central singularity in the gravitational case swallowing everything is trapped inside the horizon. Correlations however are not absent in the gravitational case: to see them one has simply to consider correlation functions at unequal times which indeed display the expected peak.