Formation of inflaton halos after inflation

TL;DR

This paper models the formation of inflaton halos after inflation during a matter-dominated epoch, using N-body simulations and analytical methods, revealing their properties, potential gravitational wave sources, and implications for early universe dynamics.

Contribution

It introduces a novel application of structure formation techniques to inflaton condensate fragmentation, providing estimates of halo properties and their effects on reheating and primordial black hole formation.

Findings

Inflaton halos can have masses up to 20 kg and radii around 10^{-20} m.

N-body simulations agree with the Press-Schechter formalism for halo mass functions.

A prolonged matter-dominated phase could influence reheating, gravitational wave production, and primordial black hole formation.

Abstract

The early Universe may have passed through an extended period of matter-dominated expansion following inflation and prior to the onset of radiation domination. Sub-horizon density perturbations grow gravitationally during such an epoch, collapsing into bound structures if it lasts long enough. The strong analogy between this phase and structure formation in the present-day universe allows the use of N-body simulations and approximate methods for halo formation to model the fragmentation of the inflaton condensate into inflaton halos. For a simple model we find these halos have masses of up to $20\,\mathrm{kg}$ and radii of the order of $10^{-20}\,\mathrm{m}$, roughly $10^{-24}$ seconds after the Big Bang. We find that the N-body halo mass function matches predictions of the mass-Peak Patch method and the Press-Schechter formalism within the expected range of scales. A long matter-dominated phase would imply that reheating and thermalization occurs in a universe with large variations in density, potentially modifying the dynamics of this process. In addition, large overdensities can source gravitational waves and may lead to the formation of primordial black holes.