Quantum fluctuating CGHS geometries and the information paradox

TL;DR

This paper investigates Hawking radiation in a quantum superposition of geometries within the 2D CGHS model, revealing non-thermal features and potential information retrieval from radiation considering backreaction effects.

Contribution

It introduces a quantum superposition of classical geometries in the CGHS model and analyzes how Hawking radiation encodes information about the collapsing shell.

Findings

Hawking radiation spectrum shows non-thermal behavior at finite times.

Late-time radiation depends only on the cosmological constant.

Information about the shell can be extracted from radiation with backreaction considerations.

Abstract

We study Hawking radiation on the quantum spacetime generated by a quantum ingoing null shell in the 2d theory proposed by Callan-Giddings-Harvey-Strominger (CGHS). The quantum spacetime is a superposition of classical geometries with uncertainty in position and momentum of the collapsing shell. The Hawking radiation spectrum is computed, revealing a non-thermal behavior for finite time as well as a dependence on the shell's physical degrees of freedom. Hawking radiation's dependence on the collapsing shell becomes irrelevant in the late time approximation as we reach $i^+$ since the radiation's temperature depends exclusively on the cosmological constant. However, we argue that the information of the quantum state of a collapsing shell can be read from the Hawking radiation if we perform measurements at $\mathcal{I_R^+}$ taking into account backreaction effects.