Firewalls From General Covariance

TL;DR

This paper argues that maintaining horizon normalcy in black hole physics requires a breakdown of general covariance far from the horizon, challenging proposals that suggest horizon normalcy persists in certain quantum states.

Contribution

It introduces the concept of horizon normalcy and demonstrates that its state-dependent preservation necessitates a breakdown of general covariance away from the black hole.

Findings

Horizon normalcy depends on the global state of radiation.

Maintaining horizon normalcy requires breaking general covariance far from the horizon.

Timefolds do not resolve the dependence of horizon normalcy on the infinite future.

Abstract

I define "horizon normalcy" as the approximate validity of Semiclassical Gravity and Effective Field Theory (SGEFT), for the description of observers that approach or cross a black hole horizon. If black holes return information, then horizon normalcy must fail substantially, at least in some global states. Proposals such as ER=EPR and nonisometric maps assert that horizon normalcy persists, so long as the Hawking radiation remains in a computationally simple state. Here I argue that state-dependent horizon normalcy - independently of the underlying mechanism, and independently of the class of radiation states asserted to guarantee normalcy - requires a breakdown of general covariance far from the black hole, or else horizon normalcy will depend on the infinite future of the exterior. This is because the radiation can be in different states at different events, all spacelike to the horizon crossing event whose normalcy is at stake. I discuss a related effect in AdS/CFT, and I argue that its resolution by timefolds is of no help here.