Entanglement islands and black hole decay in regular dilaton gravity

TL;DR

This paper studies two-dimensional dilaton gravity models, focusing on entanglement entropy and black hole decay, revealing potential breakdowns of semiclassical approximations and proposing decay mechanisms for black hole remnants.

Contribution

It introduces a detailed analysis of entanglement entropy in regular dilaton black holes and suggests a decay process for black hole remnants to address unitarity issues.

Findings

Generalized entanglement entropy diverges near extremal regular black holes.

Regular black hole remnants are likely unstable and decay via quantum fluctuations.

A semiclassical decay amplitude estimate is provided for black hole remnants.

Abstract

We consider a class of two-dimensional dilaton gravity models with linear dilaton vacuum including Callan-Giddings-Harvey-Strominger (CGHS) model as the special case. General thermodynamic properties of black holes in such models are evaluated. We focus on the CGHS model and its modification with regular black holes as empty-space solutions characterized by ever-present finite curvature. We find generalized entanglement entropy blows-up for near-extremal regular black holes considered as remnants. That signalling a possible breakdown of the semiclassical approximation near the endpoint of evaporation. We conjecture that remnants are unstable and decay by quantum fluctuations into horizonless spacetimes. We give an estimate for the decay amplitude by using a semiclassical regularization method and propose a path to mitigate the unitarity loss problem.