Title: Initial spins of primordial black holes formed with a soft equation of state
Abstract: In this talk, I will talk about the recent attempt to evaluate the probability distribution of the spins of primordial black holes (PBHs) formed in the universe dominated by a perfect fluid with the linear equation of state (EoS) p = wρ and 0<w<1/3.
Specifically, we focus on the linear-order effects of cosmological perturbations and compute the probability distribution at the turn-around time, when the fluctuation decouples from the background evolution.
Our analysis reveals that the typical PBH spin decreases with the EoS parameter w, although the dependence is not strong for 0.23<w<1/3, corresponding to the QCD phase transition.
Additionally, if time permits, I will also provide an overview of the joint distribution for spin and mass.
