Curvature Perturbation Spectrum in Two-field Inflation with a Turning Trajectory

TL;DR

This paper analyzes how a turning trajectory in two-field inflation affects the curvature perturbation spectrum, especially when the isocurvature mass is large, providing analytical corrections and confirming previous effective field theory results.

Contribution

It offers an analytical calculation of the corrections to the curvature spectrum due to heavy isocurvature modes in a two-field inflation model with a turning trajectory, extending previous work.

Findings

Corrections are proportional to M_{eff}^{-2} when M_{eff}^2>>H^2.

Analytical results agree with numerical simulations.

Results confirm previous effective field theory predictions.

Abstract

We revisit a two-component inflaton model with a turning trajectory in the field space, where the field slowly rolls down along the trajectory. We consider the case when the effective mass in the direction perpendicular to the trajectory, namely the isocurvature direction, is either of the same order as or much larger than the Hubble parameter. Assuming that the turning angular velocity is small, we compute analytically the corrections to the power spectrum of curvature perturbation caused by the mediation of the heavy isocurvature perturbation, and compare our analytic results with the numerical ones. Especially, when M_{eff}^2>>H^2, we find that it is proportional to M_{eff}^{-2}. This result is consistent with the one obtained previously by an effective field theory approach.