Studies in Small Field Inflation

TL;DR

This paper investigates small field slow roll inflation, emphasizing the role of low energy supersymmetry and constrained structures, leading to nearly inevitable hybrid inflation with specific parameter restrictions and universal spectral index predictions.

Contribution

It demonstrates that small field inflation models with low energy supersymmetry naturally lead to hybrid inflation and are characterized by a limited set of parameters, reducing fine tuning.

Findings

Hybrid inflation is nearly inevitable in small field scenarios.

The inflationary parameters are tightly constrained by slow roll conditions.

Models avoid the cosmological moduli problem.

Abstract

We explore some issues in slow roll inflation in situations where field excursions are small compared to $M_p$. We argue that for small field inflation, minimizing fine tuning requires low energy supersymmetry and a tightly constrained structure. Hybrid inflation is {\it almost} an inevitable outcome. The resulting theory can be described in terms of a supersymmetric low energy effective action and inflation completely characterized in terms of a small number of parameters. Demanding slow roll inflation significantly constrains these parameters. In this context, the generic level of fine tuning can be described as a function of the number of light fields, there is an upper bound on the scale of inflation, and an (almost) universal prediction for the spectral index. Models of this type need not suffer from a cosmological moduli problem.