Effective field theory approach to quasi-single field inflation and effects of heavy fields

TL;DR

This paper develops an effective field theory framework for quasi-single field inflation, analyzing how heavy scalar fields influence primordial fluctuations, including power spectra and non-Gaussianities, with potential applications to models with heavy particles.

Contribution

It constructs a general third-order action for quasi-single field inflation using the effective field theory approach, incorporating effects of heavy fields and trajectory turns.

Findings

Derived the power spectrum modifications due to heavy fields.

Analyzed the momentum dependence of three-point functions in the squeezed limit.

Discussed implications of heavy particles and trajectory turns during inflation.

Abstract

We apply the effective field theory approach to quasi-single field inflation, which contains an additional scalar field with Hubble scale mass other than inflaton. Based on the time-dependent spatial diffeomorphism, which is not broken by the time-dependent background evolution, the most generic action of quasi-single field inflation is constructed up to third order fluctuations. Using the obtained action, the effects of the additional massive scalar field on the primordial curvature perturbations are discussed. In particular, we calculate the power spectrum and discuss the momentum-dependence of three point functions in the squeezed limit for general settings of quasi-single field inflation. Our framework can be also applied to inflation models with heavy particles. We make a qualitative discussion on the effects of heavy particles during inflation and that of sudden turning trajectory in our framework.