Lighting the Dark: The Evolution of the Post-Inflationary Universe

TL;DR

This paper investigates the nonlinear gravitational fragmentation of the inflaton condensate after inflation using Schrödinger-Poisson equations, revealing rapid overdensity formation that impacts the early universe's power spectrum and dark matter composition.

Contribution

It introduces the first numerical study of nonlinear condensate fragmentation in the early universe, linking gravitational dynamics to inflationary and dark matter phenomenology.

Findings

Large overdensities form quickly after nonlinearity begins.

Fragmentation dynamics are well-described by Schrödinger-Poisson equations.

Implications for inflationary power spectrum and dark matter fraction.

Abstract

In simple inflationary cosmological scenarios the near-exponential growth can be followed by a long period in which the Universe is dominated by the oscillating inflaton condensate. The condensate is initially almost homogeneous, but perturbations grow gravitationally, eventually fragmenting the condensate if it is not disrupted more quickly by resonance or prompt reheating. We show that the gravitational fragmentation of the condensate is well-described by the Schr\"odinger-Poisson equations and use numerical solutions to show that large overdensities form quickly after the onset of nonlinearity. This is the first exploration of this phase of nonlinear dynamics in the very early universe, which can affect the detailed form of the inflationary power spectrum and the dark matter fraction when the dark sector is directly coupled to the inflaton.