Seminar of Theory of Relativity and Gravitation

A consistent picture of black hole formation and evaporation appears to exclude not only spacetime singularities but also event horizons, while retaining the presence of local trapping horizons. I will discuss two models that are thought to provide a path toward realizing this paradigm. The first is the nonhomogeneous dust collapse in effective loop quantum gravity, in which the collapsing matter undergoes a bounce. It has been conjectured that no event horizon forms in this scenario, instead, shock waves emerge, leading to black hole explosions. I will show, however, that the collapse cannot occur within a single asymptotic region and that event horizons are, in fact, inevitable in this model. The second model concerns the collapse of a homogeneous and isotropic dust ball into a Hayward black hole. I will demonstrate that a mechanism analogous to cosmic inflation decelerates the collapsing matter, thereby preventing singularity formation and leading instead to a perpetual 'long squeeze', where the interior is described by a quasi–de Sitter spacetime at late times. The implications of this model will be discussed in the context of the Borde–Vilenkin–Guth theorem.