Unitarity and fuzzball complementarity: "Alice fuzzes but may not even know it!"

TL;DR

This paper examines the black hole firewall argument, emphasizing that unitarity requires information to be carried by all radiation quanta, and discusses how fuzzball complementarity explains the infalling observer's experience.

Contribution

It clarifies the implications of unitarity for black hole horizons and evaluates the fuzzball complementarity proposal in describing infalling observers' experiences.

Findings

Unitarity necessitates information in all emitted radiation quanta.

An information-free horizon contradicts unitarity during evaporation.

Fuzzball microstates influence the experience of infalling detectors.

Abstract

We investigate the recent black hole firewall argument. For a black hole in a typical state we argue that unitarity requires every quantum of radiation leaving the black hole to carry information about the initial state. An information-free horizon is thus inconsistent with unitary at every step of the evaporation process (in particular both before and after Page time). The required horizon-scale structure is manifest in the fuzzball proposal which provides a mechanism for holding up the structure. In this context we want to address the experience of an infalling observer and discuss the recent fuzzball complementarity proposal. Unlike black hole complementarity and observer complementarity which postulate asymptotic observers experience a hot membrane while infalling ones pass freely through the horizon, fuzzball complementarity postulates that fine-grained operators experience the details of the fuzzball microstate and coarse-grained operators experience the black hole. In particular, this implies that an infalling detector tuned to energy E ~ T, where T is the asymptotic Hawking temperature, does not experience free infall while one tuned to E >> T does.