Firewalls as artefacts of inconsistent truncations of quantum geometries

TL;DR

This paper argues that firewalls result from inconsistent truncations of quantum effects in black hole physics, showing that proper corrections resolve divergences and smooth out the horizon, indicating firewall appearance signals semiclassical breakdown at the Page time.

Contribution

It demonstrates that firewalls are artifacts of naive truncation and that correct quantum corrections prevent divergences, resolving the firewall paradox.

Findings

Naive truncation leads to divergent energy density near the horizon.

Proper quantum corrections are suppressed far but diverge near the horizon.

Correlations remain smooth at the horizon when corrections are correctly summed.

Abstract

In this paper we argue that a firewall is simply a manifestation of an inconsistent truncation of non-perturbative effects that unitarize the semiclassical black hole. Namely, we show that a naive truncation of quantum corrections to the Hawking spectrum at order ${\cal O}(e^{-S})$, inexorably leads to a "localised'' divergent energy density near the black hole horizon. Nevertheless, in the same approximation, a distant observer only sees a discretised spectrum and concludes that unitarity is achieved by ${\cal O}(e^{-S})$ effects. This is due to the fact that instead, the correct quantum corrections to the Hawking spectrum go like ${\cal O}( g^{tt} e^{-S})$. Therefore, while at a distance far away from the horizon, where $g^{tt}\approx 1$, quantum corrections {\it are} perturbative, they {\it do} diverge close to the horizon, where $g^{tt}\rightarrow \infty$. Nevertheless, these "corrections" nicely re-sum so that correlations functions are smooth at the would-be black hole horizon. Thus, we conclude that the appearance of firewalls is just a signal of the breaking of the semiclassical approximation at the Page time, even for large black holes.