Seminarium "Teoria cząstek elementarnych i kosmologia"

Primordial Black Holes (PBHs) have recently attracted ample attention as they may explain some of the LIGO/Virgo/KAGRA observations and significantly contribute to the dark matter in our universe. The standard formation scenario assumes PBHs form out of the collapse of large radiation over-densities in the early universe. In this context, we present a new prescription to compute the abundance of PBHs mass fraction in the presence of local non-gaussianity (NG). Simultaneously, recent releases of data from multiple pulsar timing array (PTA) experiments reveal compelling evidence of Hellings-Downs angular correlations. This discovery implies that the observed stochastic common spectrum could be interpreted as a stochastic gravitational wave background. We study whether the signal may originate from gravitational waves induced by high-amplitude primordial curvature perturbations. Such large perturbations may be accompanied by the generation of a sizeable PBH abundance. We discuss in which scenarios the inclusion of non-Gaussianities in the computation of the abundance can lead to a signal compatible with the PTA experiments without overproducing PBHs.