Inflatonless Inflation

TL;DR

This paper proposes a model where extra dimensions contract and our universe inflates without the need for an inflaton field, driven by non-linear sigma fields causing dynamical compactification.

Contribution

It introduces a novel higher-dimensional Einstein gravity model with non-linear sigma fields that naturally induce inflation through dynamical compactification without inflaton particles.

Findings

Extra dimensions contract exponentially while our universe expands exponentially.

Inflation is driven by non-linear sigma fields, eliminating the need for inflaton fields.

The model provides a new mechanism for inflation via dynamical compactification.

Abstract

We consider a 4+N dimensional Einstein gravity coupled to a non-linear sigma model. This theory admits a solution in which the N extra dimensions contract exponentially while the ordinary space expand exponentially. Physically, the non-linear sigma fields induce the dynamical compactification of the extra dimensions, which in turn drives inflation. No inflatons are required.