Dynamics of trapping horizons in black hole collapse and cosmology

Ilia Musco (Observatoire de Paris)

Resumen: In this talk I will explain some aspects of my research in black hole formation, focusing in particular on the dynamics of trapping horizons. I will start explaining the concept of trapping horizons in spherical symmetry, characterizing both black hole and cosmological horizons. They make their first appearance either within the collapsing/expanding matter or where it joins on to a vacuum exterior. Ones moving outwards with respect to the matter have been proposed for replacing the global concept of an "event horizon'' in the case of dynamical black holes. Using the Misner-Sharp formalism, we have studied the causal nature of both ingoing and outgoing horizons during collapse of idealized stellar models, with two complementary approaches focusing, respectively, on null-congruence expansion and on the horizon velocity measured with respect to the matter. The stellar models are simplified, but have a physically-motivated pressure, unlike the so-called "dust'' models, and we find that this plays an important role in general. Comparison between the two complementary approaches leads to some new insights including giving pointers towards possible changes due to quantum effects if energy conditions are violated.