Inflaton Clusters and Inflaton Stars

TL;DR

This paper explores how the inflaton field can form bound structures called inflaton clusters and inflaton stars after inflation, using analogies with axion-like particle structure formation to understand nonlinear dynamics.

Contribution

It introduces the concept of inflaton clusters and inflaton stars, adapting structure formation results from axion-like particles to the post-inflationary universe.

Findings

Inflaton condensate fragments into bound clusters.

Formation of inflaton stars within clusters.

Density contrasts can reach up to 10^6.

Abstract

In a broad class of scenarios, inflation is followed by an extended era of matter-dominated expansion during which the inflaton condensate is nonrelativistic on subhorizon scales. During this phase density perturbations grow to the point of nonlinearity and collapse into bound structures. This epoch strongly resembles structure formation with ultra-light axion-like particles. This parallel permits us to adapt results from studies of cosmological structure formation to describe the nonlinear dynamics of this post-inflationary epoch. We show that the inflaton condensate fragments into "inflaton clusters", analogues of axion dark matter halos in present-day cosmology. Moreover, solitonic objects or "inflaton stars" can form inside these clusters, leading to density contrasts as large as $10^6$ in the post-inflationary universe.