Black hole inner horizon instability in classical and semiclassical gravity

ABSTRACT: In this talk I will present an overview of the instabilities related to the presence of an inner horizon, focusing in particular on the effect these can have on the evolution of the geometry as a whole.

I will begin by presenting a simple exact model of a black hole undergoing the classical mass inflation process, conveying an intuitive understanding of the origin of this instability, and describing in detail the resulting evolution of the geometry.

Then I will discuss semiclassical backreaction. First, in parallel to the Hawking evaporation of the outer horizon, I will analyse the semiclassical evolution of a classically unperturbed inner horizon. Then, I will conclude by analysing semiclassical backreaction on a classically perturbed inner horizon (undergoing mass inflation), and discuss the possible outcomes of the evolution of a generic black hole in the full semiclassical theory.