Entropy/information flux in Hawking radiation

Understand

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.