Speaker
Mr
Tomohiro Nakama
(Research Center for the Early Universe, the University of Tokyo)
Description
If the amplitude of the density perturbation is sufficiently large in some region in the early
universe dominated by radiation, this region starts to contract against pressure gradients after
the horizon reently and collapses to form a black hole (Primordial Black Hole, PBH). In order
to analyze formation process of these PBHs, in our previous paper we developed an asymptotic
expansion approach to calculate time evolution of a spherical perturbed region outside the horizon.
Our formalism is valid even when the amplitude of the perturbation is sufficiently large to form a
PBH in the end.
In this paper results of numerical computation of time evolution of the perturbed region after the
horizon reentry are presented. The initial conditions for this numerical computation are given using
our asymptotic expansion technique. By calculating time evolution of various initial perturbations,
the condition for PBH formation is investigated. We have investigated various shapes of initial
curvature profiles at once, including those profiles which were not investigated in previous works
as well as those investigated previously, and formed ”master variables” which decide if PBHs are
formed or not. This condition will be useful in computing abundance of PBHs presicely.
Primary author
Mr
Tomohiro Nakama
(Research Center for the Early Universe, the University of Tokyo)
Co-authors
Prof.
Alexander Polnarev
(Queen Mary University of London)
Prof.
Jun'ichi Yokoyama
(Research Center for the Early Universe, University of Tokyo)
Prof.
Tomohiro Harada
(Rikkyo University)
