The Page curve and baby universes

TL;DR

Recent developments in low-energy gravity have reconciled black hole thermodynamics with Hawking radiation, successfully reproducing the Page curve and offering a consistent quantum description of black hole evaporation.

Contribution

This paper reviews the new paradigm where low-energy gravity models black hole evaporation consistent with the Page curve, emphasizing operational observables in asymptotically-flat spacetimes.

Findings

Low-energy gravity provides a self-consistent description of black hole evaporation.

The Page curve is reproduced within this framework.

Operationally-defined observables can probe the entropy of Hawking radiation.

Abstract

Black hole thermodynamics suggests that, in order to describe the physics of distant observers, one may model a black hole as a standard quantum system with density of states set by the Bekenstein-Hawking entropy $S_\mathrm{BH}$. This idea has long been considered to be in strong tension with Hawking's prediction that radiation from black holes is nearly thermal, and with low-energy gravity more generally. But the past two years have shown that low-energy gravity does offer a self-consistent description of black hole evaporation consistent with the above idea, and which in particular reproduces the famous Page curve. We provide a brief overview of this new paradigm, focusing on Lorentz-signature asymptotically-flat spacetimes, and emphasising operationally-defined observables that probe the entropy of Hawking radiation.