Cosmological perturbations in $F(R)$ gravity

TL;DR

This paper explores oscillating solutions of matter density perturbations in $F(R)$ gravity models, extending previous work focused mainly on quasi-static solutions, and examines their behavior in models with singular parameter evolutions.

Contribution

It introduces an analysis of oscillating solutions in $F(R)$ gravity, which were previously underexplored, and applies approximations to study their behavior in models with singular evolutions.

Findings

Oscillating solutions in $F(R)$ gravity are characterized using new approximations.

Behavior of matter density perturbations in models with singular evolutions is analyzed.

The study broadens understanding of perturbation dynamics beyond quasi-static solutions.

Abstract

The quasi-static solutions of the matter density perturbation in $F(R)$ gravity models have been investigated in numerous papers. However, the oscillating solutions in $F(R)$ gravity models have not been investigated enough so far. In this paper, the oscillating solutions are also examined by using appropriate approximations. And the behaviors of the matter density perturbation in F(R) gravity models with singular evolutions of the physical parameters are shortly investigated as applications of the approximated calculations.