Quantum censors: backreaction builds horizons

TL;DR

This paper argues that quantum effects in semi-classical gravity naturally generate horizons, acting as quantum censors that uphold cosmic censorship and prevent observable singularities, thus supporting the robustness of classical censorship principles.

Contribution

The authors demonstrate that quantum backreaction creates horizons in semi-classical gravity, providing nonperturbative evidence for the robustness of cosmic censorship.

Findings

Quantum backreaction generates horizons in semi-classical gravity.

Quantum censors prevent violations of cosmic censorship.

A quantum Penrose inequality supports the robustness of censorship.

Abstract

Cosmic censorship posits spacetime singularities remain concealed behind event horizons, preserving the determinism of General Relativity. While quantum gravity is expected to resolve singularities, we argue that cosmic censorship remains necessary whenever spacetime has a reliable semi-classical description. Using holography to construct exact solutions to semi-classical gravity, we show backreaction of quantum matter generates horizons -- quantum censors -- to thwart potential violations of censorship. Along with a quantum Penrose inequality, this provides compelling evidence cosmic censorship is robust, even nonperturbatively, in semi-classical gravity.