Primordial black holes from metric preheating: mass fraction in the excursion-set approach

Abstract

We calculate the mass distribution of Primordial Black Holes (PBHs) produced during metric preheating. After inflation, the oscillations of the inflaton at the bottom of its potential source a parametric resonant instability for small-scale scalar perturbations, that may collapse into black holes. After reviewing in a pedagogical way different techniques that have been developed in the literature to compute mass distributions of PBHs, we focus on the excursion-set approach. We derive a Volterra integral equation that is free of a singularity sometimes encountered, and apply it to the case of metric preheating. We find that if the energy density at which the instability stops, ρ Γ , is sufficiently smaller than the one at which inflation ends, ρ end , namely if ρend /10 16 GeV) 3/2 , then PBHs dominate the universe content at the end of the oscillatory phase. This confirms the previous analysis of Ref. [1]. By properly accounting for the "cloud-in-cloud" mechanism, we find that the mass distribution is more suppressed at low masses than previously thought, and peaks several orders of magnitude above the Hubble mass at the end of inflation. The peak mass ranges from 10 g to stellar masses, giving rise to different possible cosmological effects that we discuss.

Production and evaporation of micro black holes as a link between mirror universes

“…Thus, it is possible to obtain new constraints on the primordial BHs in models with mirror matter in comparison with the known entropy bounds on primordial BHs [44]. Microscopic primordial BHs may from the preheating instability, subsequently dominate the content of the universe, and their evaporation may be the source of reheating [45][46][47].…”

Primordial blackholes from Gauss-Bonnet-corrected single field inflation

“…[39][40][41][42][43][44][45][46][47]. It is also possible to produce primordial blackholes during (p)reheating [48][49][50][51].…”