Speaker
Description
Stochastic trees describe the inflationary structure of spacetime generated by stochastic inflation as a branching process.
In this talk, I will show that a sampled implementation of the compaction function can be constructed on such trees, enabling a refined treatment of the impact of quantum diffusion on primordial black hole (PBH) formation. Type I and type II populations of PBHs can also be distinguished, and I will show how their abundances compare in a simple tilted-quantum well model of inflation. If PBHs form, they are mainly type I in the classical, drift-dominated regime, while type II PBHs become dominant as quantum diffusion takes over. In the intermediate regime, where both effects are relevant, a critical boundary emerges at which large fluctuations are generated, PBH production is enhanced, and type II PBHs dominate the overall abundance. Our results indicate that type II PBHs are a generic outcome in regimes where quantum diffusion is significant, and a comparable — or even larger — abundance of type II PBHs appears unavoidable. This raises important questions regarding the treatment of such extreme objects.