Entanglement islands and black hole decay in regular dilaton gravity

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 signaling a possible breakdown of the semiclassical approximation near the end point 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.