Scalar Perturbations Through Cycles

TL;DR

This paper analyzes how scalar perturbations evolve through cyclic cosmological models with nonsingular bounces, revealing amplification of curvature and isocurvature perturbations over cycles.

Contribution

It provides an analytical and numerical study of scalar perturbation evolution in cyclic models, highlighting the differential amplification rates of curvature and isocurvature modes.

Findings

Curvature perturbation amplitude amplifies cycle by cycle.

Isocurvature perturbations also amplify but at a slower rate.

Coupling strength influences isocurvature amplification.

Abstract

We analytically and numerically investigate the evolutions of the scalar perturbations through the cycles with nonsingular bounce. It is found that the amplitude of the curvature perturbation on large scale will be amplified cycle by cycle, and the isocurvature perturbations also obtain an amplification, but the rate of its amplification is slower than that of curvature perturbation, unless its coupling to the metric perturbation is not negligible.