Dark Matter from Eternity

Abstract

We propose that the totality of dark matter in the universe might ascribe its origin to one of the key properties of cosmological inflation, that it may be eternal: regions that at the end of the primordial accelerated expansion of the universe never reheated, but keep eternally inflating, manifest themselves as primordial black holes in our observable universe. This mechanism can provide a primordial black hole abundance which is larger than the standard one due to the gravitational collapse of sizeable overdensities in the radiation phase. It also predicts a broad spectrum for the curvature perturbation and a flat stochastic gravitational wave background at a level of $\Omega_\text{GW} h^2 \simeq 10^{-10}$ up to the mHz.