# Post-inflationary structure formation boosted by parametric self-resonance

**Authors:** Benedikt Eggemeier, Peter Hayman, Jens C. Niemeyer, Richard Easther  
**arXiv:** [2311.08780](https://arxiv.org/abs/2311.08780)  
**Date:** 2023-11-15  
**Summary page:** https://www.summarizepaper.com/fr/arxiv-id/2311.08780v2/

## Abstract

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 Schr\"odinger-Poisson description that accurately captures the gravitational dynamics when most quanta are nonrelativistic. We consider a representative example in which resonance generates $\mathcal{O}(10^{-1})$ 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 $10^{-27}\,\mathrm{m}$, greatly extending the possible scope of nonlinear post-inflationary gravitational dynamics.