How Black Holes Burn

TL;DR

This paper calculates the rate at which information is released from a black hole during evaporation, extending Hawking's theory to include quantum fluctuations and back-reaction, and shows how the radiation purifies over time.

Contribution

It introduces a detailed model of black hole radiation that accounts for quantum effects and proposes a maximal information release rate, contrasting with previous unitarity-based predictions.

Findings

Radiation purifies continuously when phases and amplitudes are recorded.

Purification occurs only near the end if phases are not tracked, and it happens rapidly.

The study relates purity and participation ratio to the Renyi entropy of emitted radiation.

Abstract

We present a calculation of the rate of information release from a Schwarzschild BH. We have recently extended Hawking's theory of black hole (BH) evaporation to account for quantum fluctuations of the background geometry, as well as for back-reaction and time-dependence effects. Our main result has been a two-point function matrix for the radiation that consists of Hawking's thermal matrix plus off-diagonal corrections that are initially small and become more important as the evaporation proceeds. Here, we show that, if the phases and amplitudes of the radiation matrix are recorded over the lifetime of the BH, then the radiation purifies in a continuous way. We conjecture that our results establish the maximal rate at which information can be released from a semiclassical BH, to be contrasted with the minimal rate that was predicted by Page on the basis of generic unitarity arguments. When the phases of the radiation matrix are not tracked, we show that it purifies only parametrically close to the end of the BH evaporation and does so extremely fast. Our main technical tool in the quantitative treatment of this purification is the purity of the radiation matrix and, its inverse, the participation ratio. These can be related to the Renyi entropy of the density matrix of the emitted radiation.