On the Realization of Assisted Inflation

TL;DR

This paper explores conditions for successful assisted inflation, extending its applicability beyond exponential potentials to chaotic models, and shows how extra dimensions can facilitate inflation without fine-tuning.

Contribution

It generalizes assisted inflation to include chaotic potentials and demonstrates how extra dimensions can naturally enable inflation without fine-tuning.

Findings

Assisted inflation can work with chaotic potentials like  and m.

Extra dimensions can eliminate the need for fine-tuned couplings in inflation models.

In 4D theories, assisted sectors may hinder inflation unless decoupled.

Abstract

We consider conditions necessary for a successful implementation of so-called assisted inflation. We generalize the applicability of assisted inflation beyond exponential potentials as originally proposed to include standard chaotic (\lambda \phi^4 or m^2 \phi^2) models as well. We also demonstrate that in a purely 4-dimensional theory, unless the assisted sector is in fact decoupled, the additional fields of the assisted sector actually impede inflation. As a specific example of an assisted sector, we consider a 5-dimensional KK model for which the extra dimension may be somewhat or much larger than the inverse Planck scale. In this case, the assisted sector (coming from a KK compactification) eliminates the need for a fine-tuned quartic coupling to drive chaotic inflation. This is a general result of models with one or more "large" extra dimensions.