Cosmological and Solar System Consequences of f(R,T) Gravity Models

TL;DR

This paper explores various f(R,T) gravity models using dynamical systems to analyze cosmological parameters, identifying models consistent with observations and discussing implications for dark energy, the coincidence problem, and late-time universe behavior.

Contribution

It introduces new cosmological parameter analyses for f(R,T) models, identifies models aligning with observational data, and examines late-time attractor solutions in non-flat FLRW universes.

Findings

Model with n=-0.9 shows better consistency with data.

The coincidence problem is not a unique event, occurring also in the early universe.

The model R + c1√(-T) has a late-time attractor with w_DE = -1/2.

Abstract

To find more deliberate f(R,T) cosmological solutions, we proceed our previous paper further by studying some new aspects of the considered models via investigation of some new cosmological parameters/quantities to attain the most acceptable cosmological results. Our investigations are performed by applying the dynamical system approach. We obtain the cosmological parameters/quantities in terms of some defined dimensionless parameters that are used in constructing the dynamical equations of motion. The investigated parameters/quantities are the evolution of the Hubble parameter and its inverse, the "weight function", the ratio of the matter density to the dark energy density and its time variation, the deceleration, the jerk and the snap parameters, and the equation-of-state parameter of the dark energy. We numerically examine these quantities for two general models $R+\alpha R^{-n}+\sqrt{-T}$ and $R\log{[\alpha R]}^{q}+\sqrt{-T}$. All considered models have some inconsistent quantities (with respect to the available observational data), except the model with n=-0.9 which has more consistent quantities than the other ones. By considering the ratio of the matter density to the dark energy density, we find that the coincidence problem does~not refer to a unique cosmological event, rather, this coincidence also occurred in the early universe. We also present the cosmological solutions for an interesting model $R+c_{1}\sqrt{-T}$ in the non--flat FLRW metric. We show that this model has an attractor solution for the late times, though with $w^{(\textrm{DE})}=-1/2$. This model indicates that the spatial curvature density parameter gets negligible values until the present era, in which it acquires the values of the order $10^{-4}$ or $10^{-3}$. As the second part of this work, we consider the weak-field [It continues ...]