Last gasp of a black hole: unitary evaporation implies non-monotonic mass loss

TL;DR

This paper demonstrates that in a two-dimensional black hole model, unitarity and vacuum correlation restoration require the black hole to emit negative energy bursts, causing a temporary mass increase before complete evaporation.

Contribution

It reveals that unitarity constraints lead to non-monotonic mass loss, including negative energy emissions, which is a novel insight into black hole evaporation dynamics.

Findings

Black holes emit negative energy bursts during evaporation.

Mass of the black hole can temporarily increase due to negative energy emission.

Unitarity imposes constraints on the mass loss rate of black holes.

Abstract

We show within the usual two-dimensional approximation that unitarity and the restoration of Minkowski vacuum correlations at the end of black hole evaporation impose unexpected constraints on its mass loss rate: before disappearing the black hole emits one or more negative energy burst, leading to a temporary increase of its mass.