Small free field inflation in higher curvature gravity

TL;DR

This paper demonstrates that higher curvature gravity corrections can enable small field inflation with a free scalar, avoiding super-Planckian field values typical in standard models.

Contribution

It introduces a mechanism within Geometric Inflation models that allows small field inflation with a free scalar, unlike traditional large field inflation models.

Findings

Inflation can occur with sub-Planckian scalar field values.

Explicit models illustrating the mechanism are provided.

Open questions remain regarding perturbations in this regime.

Abstract

Within General Relativity, a minimally coupled scalar field governed by a quadratic potential is able to produce an accelerated expansion of the universe provided its value and excursion are larger than the Planck scale. This is an archetypical example of the so called large field inflation models. We show that by including higher curvature corrections to the gravitational action in the form of the Geometric Inflation models, it is possible to obtain accelerated expansion with a free scalar field whose values are well below the Planck scale, thereby turning a traditional large field model into a small field one. We provide the conditions the theory has to satisfy in order for this mechanism to operate, and we present two explicit models illustrating it. Finally, we present some open questions raised by this scenario in which inflation takes place completely in a higher curvature dominated regime, such as those concerning the study of perturbations.