Cosmological perturbation with two scalar fields in reheating after inflation

TL;DR

This paper studies how two scalar fields behave during the reheating phase after inflation, focusing on metric perturbations and the amplification of iso-curvature modes due to parametric resonance.

Contribution

It provides an exact solution for long-wavelength cosmological perturbations in a two-scalar field model during reheating, highlighting the resonance effects on metric perturbations.

Findings

Oscillating inflaton causes parametric resonance of scalar fields.

Iso-curvature modes of metric perturbations are amplified.

Exact solutions relate perturbations to background quantities.

Abstract

We investigate the cosmological perturbation of two-scalar field model during the reheating phase after inflation. Using the exact solution of the perturbation in long-wavelength limit, which is expressed in terms of the background quantities, we analyze the behavior of the metric perturbation. The oscillating inflaton field gives rise to the parametric resonance of the massless scalar field and this leads to the amplification of the iso-curvature mode of the metric perturbations.