Effective field theory of non-attractor inflation

Mohammad Akhshik,Hassan Firouzjahi,Sadra Jazayeri

doi:10.1088/1475-7516/2015/07/048

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 η. 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.

Highlights

The basic predictions of models of inflation are well consistent with cosmological observations [1, 2]
The large scale curvature perturbations generated from quantum fluctuations during inflation are nearly scale-invariant, nearly adiabatic and nearly Gaussian as verified very accurately in recent cosmological observations
It is known that models of single field slow-roll inflation follow the Maldacena’s consistency condition [10, 11] in which the amplitude of non-Gaussianity fNL in the squeezed limit is related to the spectral index of curvature perturbation power spectrum ns via fNsqL ∼ ns − 1.1

Summary

Introduction

The basic predictions of models of inflation are well consistent with cosmological observations [1, 2]. It is known that models of single field slow-roll inflation follow the Maldacena’s consistency condition [10, 11] in which the amplitude of non-Gaussianity fNL in the squeezed limit is related to the spectral index of curvature perturbation power spectrum ns via fNsqL ∼ ns − 1.1. This has led to the conclusion that a detection of local type non-Gaussianity at the order fNL = O(1) will rule out all single field models of inflation. The other branch of non-attractor scenarios is new which escaped the previous model-dependent studies

The non-attractor inflation in EFT setup

Power spectrum

Bispectrum

Summary and Discussions

A The quadratic and cubic actions