Chaotic inflation limits for non-minimal models with a Starobinsky attractor

TL;DR

This paper explores the behavior of non-minimal inflation models in two limits, revealing how they connect to Starobinsky and chaotic inflation, and highlighting differences in their attractor properties and observational constraints.

Contribution

It demonstrates the transition between Starobinsky and chaotic inflation in non-minimal models and analyzes the impact of conformal factor flatness on inflationary attractors.

Findings

Steep limit models yield Starobinsky inflation behavior.

Flat limit models lead to chaotic inflation behavior.

Inflation scale depends on conformal factor details in the chaotic attractor.

Abstract

We investigate inflationary attractor points by analyzing non-minimally coupled single field inflation models in two opposite limits; the `flat' limit in which the first derivative of the conformal factor is small and the `steep' limit, in which the first derivative of the conformal factor is large. We consider a subset of models that yield Starobinsky inflation in the steep conformal factor, strong coupling, limit and demonstrate that they result in chaotic inflation in the opposite flat, weak coupling, limit. The suppression of higher order powers of the inflaton field in the potential is shown to be related to the flatness condition on the conformal factor. We stress that the chaotic attractor behaviour in the weak coupling limit is of a different, less universal, character than the Starobinsky attractor. Agreement with the COBE normalisation cannot be obtained in both attractor limits at the same time and in the chaotic attractor limit the scale of inflation depends on the details of the conformal factor, contrary to the strong coupling Starobinsky attractor.