Quantized fields and gravitational particle creation in f(R) expanding universes

TL;DR

This paper investigates how quantum fields are affected by f(R) gravity in expanding universes, revealing that massless particles can be created during the early universe, unlike in standard general relativity.

Contribution

It demonstrates that in f(R) gravity, conformal invariance does not prevent massless particle creation during the radiation era, contrasting with predictions from general relativity.

Findings

Massless particles can be created in f(R) models during early universe.

Conformal invariance does not inhibit particle creation in f(R) gravity.

Differences from general relativity in cosmological particle production.

Abstract

The problem of cosmological particle creation for a spatially flat, homogeneous and isotropic Universes is discussed in the context of f(R) theories of gravity. Different from cosmological models based on general relativity theory, it is found that a conformal invariant metric does not forbid the creation of massless particles during the early stages (radiation era) of the Universe.