Title: Gravitational Waves from the Early Universe: A Primordial Black Hole Perspective
Speaker: Xinpeng Wang (IPMU)
Abstract:
Gravitational waves offer a unique window into the early Universe and the dark sector. In this talk, I will discuss gravitational wave signals associated with macroscopic dark matter, focusing in particular on primordial black holes (PBHs) and the physical phenomena linked to their formation and evolution.
PBHs can arise from the collapse of overdense Hubble patches due to an enhanced primordial power spectrum of scalar perturbations. Beyond being a compelling dark matter candidate, PBHs can leave distinctive gravitational wave signatures that provide indirect evidence of their existence.
In the first part of the talk, I will present mechanisms that generate PBHs during inflation and the associated observational consequences. In the second part, I will introduce an alternative formation channel driven by minihalo bound by long-range dark forces formed during the radiation-dominated era, along with the gravitational waves emitted by the resulting minihalo mergers. Finally, I will discuss constraints on inflationary models based on the hypothesis that PBHs may account for the mass-gap black hole events observed by LIGO/Virgo/Kagra.