Simulations of primordial black hole (PBH) formation are crucial for understanding the initial conditions that lead to black hole formation and for studying their properties and cosmological impact. Recently, a class of curvature perturbations known as type-II fluctuations, characterised by a non-monotonic areal radius, has attracted growing interest. However, when simulating PBH formation from type-II fluctuations using the standard Misner-Sharp approach, the evolution equations contain divergent terms (of the form 0/0), which hinder numerical progress and make the simulation impossible. In this talk, I will present a new methodology with the Misner-Sharp formalism that enables simulations of PBH formation from generic curvature fluctuations while avoiding the divergences associated with type-II curvature profiles. With the new method, we systematically study the black hole formation threshold across various fluctuation profiles and find that, for sufficiently large curvatures in the linear component of the compaction function shape around its peak, the threshold generally lies deep within the type-II regime. Furthermore, I will present an analytical formula that estimates the threshold in these cases.
References: ArXiv:2504.05813 , ArXiv:2504.05814

Biography

Albert Escrivà received his Ph.D. from the University of Barcelona and is currently an Assistant Professor at Nagoya University. His research focuses on Primordial Black Holes, particularly their formation through relativistic numerical simulations. Previously, he held postdoctoral positions at the National Astronomical Observatory of Japan (NAOJ) in Tokyo, was a JSPS Fellow at Nagoya University, and conducted postdoctoral research at the Université Libre de Bruxelles. 

Inviter: Shi Pi