Postinflationary structure formation boosted by parametric self-resonance

The post-inflationary Universe can pass through a long epoch of effective matter-dominated expansion.This era may allow for both the parametric amplification of initial fluctuations and the gravitational collapse of inflaton perturbations.We perform first-of-their-kind high-resolution simulations that span the resonant phase and the subsequent gravitational collapse of the inflaton field by seguing from a full Klein-Gordon treatment of resonance to a computationally efficient Schrödinger-Poisson description that accurately captures the gravitational dynamics when most quanta are nonrelativistic.We consider a representative example in which resonance generates O(10 -1 ) overdensities and gravitational collapse follows promptly as resonance ends.We observe the formation of solitonic cores inside inflaton halos and complex gravitational dynamics on scales of 10 -27 m, greatly extending the possible scope of nonlinear post-inflationary gravitational dynamics.