The gravitino problem in Extended Gravity cosmologies

TL;DR

This paper explores how extended gravity theories like $f(R)$ and $f(\mathcal{T})$ modify the universe's expansion, potentially solving the gravitino overabundance problem by making gravitino abundance independent of reheating temperature.

Contribution

It demonstrates that specific extended gravity models can naturally prevent gravitino overproduction, offering a new approach to cosmological and particle physics challenges.

Findings

$f(R)$ models can eliminate late-time gravitino abundance.

Gravitino abundance becomes independent of reheating temperature in these models.

Extended gravity corrections can address cosmological and particle physics issues.

Abstract

The gravitino problem is investigated in the framework of Extended Gravity cosmologies. In particular, we consider $f(R)$ gravity, the most natural extension of the Hilbert-Einstein action, and $f(\cal T)$ gravity, the extension of teleparallel equivalent gravity. Since in these theories the expansion laws of the Universe are modified, as compared to the standard $\Lambda$CDM cosmology, it follows that also the thermal history of particles gets modified. We show that $f(R)$ models allow to avoid the late abundance of gravitinos. In particular, we found that for an appropriate choice of the parameters characterizing the $f(R)$ model, the gravitino abundance turns out to be independent of the reheating temperature. A similar behavior is achieved also in the context of $f(\cal T)$ gravity. In this perspective, we can conclude that geometric corrections to standard General Relativity (and to Teleparallel Equivalent of General Relativity) can improve shortcomings both in cosmology and in unified theories beyond the Standard Model of particles.