Inflating an Inhomogeneous Universe

TL;DR

This paper investigates how initial inhomogeneities affect the onset of inflation in multifield cosmological models using lattice simulations, revealing that small inhomogeneities can significantly influence inflation outcomes.

Contribution

It provides a qualitative lattice-based analysis of inflation initiation in multifield models, highlighting the impact of subhorizon inhomogeneities on inflation success.

Findings

Small inhomogeneities influence whether inflation begins in multifield scenarios.

Some initial configurations that do not inflate homogeneously can succeed when inhomogeneity is included.

Other configurations that inflate homogeneously fail when inhomogeneity is added.

Abstract

While cosmological inflation can erase primordial inhomogeneities, it is possible that inflation may not begin in a significantly inhomogeneous universe. This issue is particularly pressing in multifield scenarios, where even the homogeneous dynamics may depend sensitively on the initial configuration. This paper presents an initial survey of the onset of inflation in multifield models, via qualitative lattice-based simulations that do not include local gravitational backreaction. Using hybrid inflation as a test model, our results suggest that small subhorizon inhomogeneities do play a key role in determining whether inflation begins in multifield scenarios. Interestingly, some configurations which do not inflate in the homogeneous limit "succeed" after inhomogeneity is included, while other initial configurations which inflate in the homogeneous limit "fail" when inhomogeneity is added.