Sustainability of multi-field inflation and bound on string scale

TL;DR

This paper investigates how interactions between multiple inflaton fields affect inflation duration and derives bounds on the string scale, suggesting it must exceed the GUT scale to sustain sufficient inflation.

Contribution

It introduces a bound on the string scale based on multi-field inflation dynamics with interaction effects, linking inflationary behavior to fundamental theory scales.

Findings

Interactions reduce the total number of e-folds significantly.

A lower bound on the string scale is established, exceeding the GUT scale.

Multi-field inflation models can constrain underlying fundamental theories.

Abstract

We study the effects of the interaction terms between the inflaton fields on the inflationary dynamics in multi-field models. With power law type potential and interactions, the total number of e-folds may get considerably reduced and can lead to unacceptably short period of inflation. Also we point out that this can place a bound on the characteristic scale of the underlying theory such as string theory. Using a simple multi-field chaotic inflation model from string theory, the string scale is constrained to be larger than the scale of grand unified theory.