No Cosmic Rays from Curvature Oscillations during Structure Formation with $F(R)$-gravity

TL;DR

This paper reevaluates the potential for curvature oscillations in $F(R)$-gravity models to produce cosmic rays during structure formation, concluding that particle production is negligible when more accurate methods are used.

Contribution

It demonstrates that previous estimates of high-energy particle production from curvature oscillations are invalid due to oversimplified assumptions, providing a more precise analysis in the Einstein frame.

Findings

Particle production rate is negligible when proper calculations are performed.

The continuous matter density approximation is invalid for these models.

Curvature oscillations do not significantly contribute to cosmic ray flux.

Abstract

The Starobinsky model of modified gravity suggested to explain dark energy may be also considered in the astrophysical context. Recently it has been pointed out that in contracting regions curvature oscillations around the GR value may lead to the production of high energy particles which contribute to the cosmic ray flux. We revisit these calculations in the Einstein frame and show that the continuous approximation for the matter density used in the original calculations is not valid. We show that this problem is generic in $F(R)$-gravity models introduced to describe the dark energy. We go beyond the approximation and find the rate of particle production to be negligible.