Cosmological evolution in R^2 gravity

TL;DR

This paper investigates the evolution of the universe during the radiation epoch within R^2 gravity, solving equations analytically and numerically, and explores implications for non-thermal dark matter creation.

Contribution

It provides a detailed analysis of cosmological evolution in R^2 gravity, including particle production and back reaction effects, which are novel in this context.

Findings

Analytical and numerical solutions for R and H during radiation epoch

Calculation of particle production rate by oscillating curvature

Discussion on non-thermal dark matter creation mechanisms

Abstract

The Universe evolution during the radiation-dominated epoch in the R^2-extended gravity theory is considered. The equations of motion for R and H are solved analytically and numerically. The particle production rate by the oscillating curvature is calculated in one-loop approximation and the back reaction of particle production on the evolution of R is taken into account. Possible implications of the model for cosmological creation of non-thermal dark matter is discussed.