Quantum fluctuating CGHS geometries and the information paradox

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.