Quantum hair of black holes out of equilibrium

TL;DR

This paper demonstrates that out-of-equilibrium quantum black holes can emit large-amplitude Hawking radiation, revealing internal information through a new form of quantum hair detectable via gravitational waves.

Contribution

It introduces a model-independent quantum hair for out-of-equilibrium black holes, enabling internal state detection through enhanced Hawking radiation.

Findings

Out-of-equilibrium black holes emit larger Hawking radiation.

The new quantum hair reveals black hole interior information.

Detection possible via gravitational wave emission.

Abstract

Classically, the black hole (BH) horizon is completely opaque, hiding any clues about the state and very existence of its interior. Quantum mechanically and in equilibrium, the situation is not much different: Hawking radiation will now be emitted, but it comes out at an extremely slow rate, is thermal to a high degree of accuracy and thus carries a minimal amount of information about the quantum state within the BH. Here, it is shown that the situation is significantly different when a quantum BH is out of equilibrium. We argue that the BH can then emit "supersized" Hawking radiation with a much larger amplitude than that emitted in equilibrium. The result is a new type of quantum hair that can reveal the state and composition of the BH interior to an external observer. Moreover, the frequency and amplitude of the new hair can be explained by the observer without invoking any new physical principles. The new hair decays at a parametrically slow rate in comparison to the Schwarzschild time scale and can be detected through the emission of gravitational waves (and possibly other types of waves); for example, during and after a BH-merger event. The current discussion is motivated by a previous analysis, in the context of a recently proposed polymer model for the BH interior, that implies emissions just like those described here. We expect, however, that the new hair is a model-independent property of quantum BHs.