Scalaron production in contracting astrophysical objects

TL;DR

This paper investigates scalaron particle creation during contraction in a modified gravity model, finding negligible particle production within realistic parameters, with implications for cosmic ray flux and early universe physics.

Contribution

It provides an analytical calculation of scalaron production during contraction in F(R)-gravity, showing it is negligible for viable model parameters.

Findings

Scalaron production during contraction is negligible for realistic parameters.

Heavy scalarons could decay and contribute to cosmic rays.

Results likely extend to generic F(R)-gravity models.

Abstract

We study the creation of high energy SM particles in the Starobinsky model of dark energy (a variant of F(R)-gravity) inside the regions contracting due to the Jeans instability. In this modification of gravity the additional degree of freedom -- scalaron -- behaves as a particle with mass depending on matter density. So when the mass changes light scalarons could be created at a non-adiabatic stage. Later scalaron mass grows and could reach large values, even the value of 10^{13} GeV, favored by early-time inflation. Heavy scalarons decay contributing to the cosmic ray flux. We analytically calculated the number density of created particles for the case of exponential (Jeans) contraction and found it negligibly small provided the phenomenologically viable and cosmologically interesting range of model parameters. We expect similar results for a generic model of F(R)-gravity mimicking cosmological constant.