Cosmology in modified $f(R,T)$-gravity

TL;DR

This paper proposes a modified $f(R,T)$-gravity theory with higher derivatives of matter fields, analyzing its stability, cosmological implications, and demonstrating natural inflationary scenarios compatible with observations.

Contribution

It introduces a new $f(R,T)$-gravity model with higher derivatives, providing stability analysis and showing natural inflation without extra matter.

Findings

Stability conditions restrict model parameters to avoid instabilities.

The theory naturally produces inflationary scenarios in dust-filled universes.

The inflationary model aligns well with observational data.

Abstract

In present paper we propose further modification of $f(R,T)$-gravity (where $T$ is trace of energy-momentum tensor) by introducing higher derivatives matter fields. We discuss stability conditions in proposed theory and find restrictions for parameters to prevent appearance of main type of instabilities, such as ghost-like and tachyon-like instabilities. We derive cosmological equations for a few representations of theory and discuss main differences with convenient $f(R,T)$-gravity without higher derivatives. It is demonstrated that in presented theory inflationary scenarios appears quite naturally even in the dust-filled Universe without any additional matter sources. Finally we construct inflationary model in one of the simplest representation of the theory, calculate main inflationary parameters and find that it may be in quite agreement with observations.