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

Understand

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.