Effective Field Theory of non-Attractor Inflation

TL;DR

This paper develops an effective field theory framework for non-attractor inflation, identifying two solution branches with distinct behaviors of curvature perturbations and non-Gaussianity, expanding understanding of inflationary models.

Contribution

It introduces a model-independent EFT approach to non-attractor inflation, discovering two solution branches with unique super-horizon behaviors and non-Gaussianity characteristics.

Findings

Two independent branches of non-attractor inflation solutions identified.

First branch extends previous models with non-frozen curvature perturbations.

Second branch shows frozen curvature perturbations with variable bispectrum shapes.

Abstract

We present the model-independent studies of non attractor inflation in the context of effective field theory (EFT) of inflation. Within the EFT approach two independent branches of non-attractor inflation solutions are discovered in which a near scale-invariant curvature perturbation power spectrum is generated from the interplay between the variation of sound speed and the second slow roll parameter \eta. The first branch captures and extends the previously studied models of non-attractor inflation in which the curvature perturbation is not frozen on super-horizon scales and the single field non-Gaussianity consistency condition is violated. We present the general expression for the amplitude of local-type non-Gaussianity in this branch. The second branch is new in which the curvature perturbation is frozen on super-horizon scales and the single field non-Gaussianity consistency condition does hold in the squeezed limit. Depending on the model parameters, the shape of bispectrum in this branch changes from an equilateral configuration to a folded configuration while the amplitude of non-Gaussianity is less than unity.