Primordial Black Holes from Kinetic Preheating

TL;DR

This paper shows that kinetic preheating after inflation can produce micro black holes through nonlinear field fluctuations, affecting early Universe dynamics and reheating without needing large initial curvature perturbations.

Contribution

It introduces a novel mechanism for black hole formation during preheating in inflationary models with derivative couplings, supported by fully relativistic simulations.

Findings

Black holes of tens of grams can form shortly after inflation.

These black holes evaporate rapidly via Hawking radiation.

Black hole formation influences the post-inflationary equation of state.

Abstract

We demonstrate that violent kinetic preheating following inflation can lead to the formation of black holes in the early Universe. In $\alpha$-attractor models with derivative inflaton couplings, nonlinear amplification of field fluctuations drives large spacetime curvature and gravitational collapse shortly after inflation ends. Using fully general-relativistic lattice simulations, we find that these dynamics produce black holes with masses of order tens of grams at sub-horizon scales, without requiring large primordial curvature perturbations. Although such micro-black holes evaporate rapidly via Hawking radiation, their formation modifies the post-inflationary equation of state and their evaporation can successfully reheat the Universe before Big Bang nucleosynthesis. These results identify kinetic preheating as a new, efficient channel for black-hole production and establish a direct connection between inflationary symmetries and strong-gravity phenomena at reheating.