The flaw in the firewall argument

TL;DR

This paper clarifies black hole complementarity by analyzing the mechanisms ensuring unitarity, showing that high-energy quanta enable a consistent complementary description and addressing recent criticisms.

Contribution

It introduces a detailed mechanism involving energy scales and horizon dynamics that supports black hole complementarity, countering recent arguments against it.

Findings

High-energy Hawking quanta carry information.

The stretched horizon expands to accommodate infalling bits.

Infalling quanta interact mainly within a small distance from the horizon.

Abstract

A lot of confusion surrounds the issue of black hole complementarity, because the question has been considered without discussing the mechanism which guarantees unitarity. Considering such a mechanism leads to the following: (1) The Hawking quanta with energy E of order the black hole temperature T carry information, and so only appropriate processes involving E>>T quanta can have any possible complementary description with an information-free horizon; (2) The stretched horizon describes all possible black hole states with a given mass M, and it must expand out to a distance s_{bubble} before it can accept additional infalling bits; (3) The Hawking radiation has a specific low temperature T, and infalling quanta interact significantly with it only within a distance s_{alpha} of the horizon. One finds s_{alpha} << s_{bubble} for E>>T, and this removes the argument against complementarity recently made by Almheiri et al. In particular, the condition E>>T leads to the notion of 'fuzzball complementarity', where the modes around the horizon are indeed correctly entangled in the complementary picture to give the vacuum.