Evolution of Cosmological Perturbation in Reheating Phase of the Universe

TL;DR

This paper investigates how cosmological perturbations evolve during the reheating phase of the universe, showing that parametric resonance can cause density perturbations to grow significantly, especially with power-law inflaton potentials.

Contribution

It demonstrates that the evolution of perturbations during reheating can be described by the Mathieu equation, revealing the role of parametric resonance in density growth.

Findings

Density perturbations grow via parametric resonance.

The evolution reduces to the Mathieu equation for power-law potentials.

Perturbation growth is significant during the oscillatory reheating stage.

Abstract

The evolution of the cosmological perturbation during the oscillatory stage of the scalar field is investigated. For the power law potential of the inflaton field, the evolution equation of the Mukhanov's gauge invariant variable is reduced to the Mathieu equation and the density perturbation grows by the parametric resonance.