Paolo Meda (Genova University)

Evaporation of four-dimensional black holes induced by the trace anomaly in semiclassical gravity 

A first approximation to describe the interplay between quantum matter and gravity is given by the quantum field theory on curved spacetimes and the semiclassical gravity, in which the backreaction of a quantum matter field propagating over a fixed spacetime geometry is studying using the so-called semiclassical Einstein equation. In this framework, the evaporation of four-dimensional spherically symmetric black holes can be explained by the appearance of an ingoing negative energy flux at the apparent horizon, which induces a negative variation of the black hole mass. I will show that this flux can be sourced by the trace anomaly of the quantum stress-energy tensor in case of a massless conformally-coupled scalar field once a certain averaged energy condition is assumed outside the horizon. As an example, I will compute the negative flux and the rate of evaporation in the Vaidya spacetime, which describes the exterior geometry of a null radiating star.