Entropy/information flux in Hawking radiation

TL;DR

This paper investigates the entropy and information flow in Hawking radiation, demonstrating that unitarity implies a balanced entropy/information budget, using an extended tripartite model based on Page's approach.

Contribution

It extends the average subsystem approach to a tripartite system, providing a new framework for analyzing entropy and information in black hole radiation.

Findings

Entropy per photon in Hawking radiation is consistent with unitarity.

The tripartite model accounts for environmental influence on entropy/information balance.

Supports the idea that black hole evaporation preserves information.

Abstract

Blackbody radiation contains (on average) an entropy of 3.9\pm2.5 bits per photon. If the emission process is unitary, then this entropy is exactly compensated by "hidden information" in the correlations. We extend this argument to the Hawking radiation from GR black holes, demonstrating that the assumption of unitarity leads to a perfectly reasonable entropy/information budget. The key technical aspect of our calculation is a variant of the "average subsystem" approach developed by Page, which we extend beyond bipartite pure systems, to a tripartite pure system that considers the influence of the environment.