Super-Horizon Scale Dynamics of Multi-Scalar Inflation

TL;DR

This paper develops a method to analyze super-horizon scale perturbations in multi-scalar inflation, connecting background solutions with perturbation equations and extending to nonlinear dynamics.

Contribution

It introduces a novel approach to solve super-horizon perturbations using background solutions and extends the formalism to nonlinear regimes.

Findings

Method links perturbation equations to background solutions.

Strategy for nonlinear super-horizon perturbation analysis.

Clarifies relation between long wavelength limit and background dynamics.

Abstract

We consider the dynamics of a multi-component scalar field on super-horizon scales in the context of inflationary cosmology. We present a method to solve the perturbation equations on super- horizon scales, i.e., in the long wavelength limit, by using only the knowledge of spatially homogeneous background solutions. In doing so, we clarify the relation between the perturbation equations in the long wavelength limit and the background equations. Then as a natural extension of our formalism, we provide a strategy to study super-horizon scale perturbations beyond the standard linear perturbation theory. Namely we reformulate our method so as to take into account the nonlinear dynamics of the scalar field.