Routing (electronic design automation)

Quantum mechanics

Micro black hole

Theoretical physics

Philosophy

Mathematical physics

Quantum gravity

Entropy (arrow of time)

Archaeology

Computer science

Visual arts

Simple (philosophy)

Black hole information paradox

Black hole thermodynamics

Computer network

Routing protocol

Superselection

Physics

Replica

Hawking radiation

Geography

Wormhole

Political science

Link-state routing protocol

Epistemology

Unitary state

Quantum

Black hole (networking)

Hawking

Journal of High Energy Physics

A bstract We reformulate recent insights into black hole information in a manner emphasizing operationally-defined notions of entropy, Lorentz-signature descriptions, and asymptotically flat spacetimes. With the help of replica wormholes, we find that experiments of asymptotic observers are consistent with black holes as unitary quantum systems, with density of states given by the Bekenstein-Hawking formula. However, this comes at the cost of superselection sectors associated with the state of baby universes. Spacetimes studied by Polchinski and Strominger in 1994 provide a simple illustration of the associated concepts and techniques, and we argue them to be a natural late-time extrapolation of replica wormholes. The work aims to be self-contained and, in particular, to be accessible to readers who have not yet mastered earlier formulations of the ideas above.

Observations of Hawking radiation: the Page curve and baby universes