An Apologia for Firewalls

TL;DR

The paper argues that popular resolutions to the black hole information paradox—such as embedding the interior in early radiation or employing nonviolent nonlocality—are incompatible with quantum mechanics or black hole entropy bounds when examined through AdS/CFT. By analyzing evaporating AdS black holes and both evaporating and static scenarios, the authors show that purity, EFT, and no-drama cannot all hold for old or large black holes without invoking dramatic modifications to quantum mechanics for infalling observers. They present multiple counting arguments and energy-entropy constraints that favor firewall-like drama at the horizon as a generic feature, unless a profound nonperturbative understanding of gravity alters the current framework. The work thereby constrains proposed firewall evasions and underscores the need for a deeper theory of bulk quantum gravity to resolve the paradox.

Abstract

We address proposed alternatives to the black hole firewall. We show that embedding the interior Hilbert space of an old black hole into the Hilbert space of the early radiation is inconsistent, as is embedding the semi-classical interior of an AdS black hole into any dual CFT Hilbert space. We develop the use of large AdS black holes as a system to sharpen the firewall argument. We also reiterate arguments that unitary non-local theories can avoid firewalls only if the non-localities are suitably dramatic.