Cosmological and solar system consequences off(R,T)gravity models

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 + αR −n + √ −T and R log [αR] q + √ −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+c1 √ −T in the non-flat FLRW metric. We show that this model has an attractor solution for the late times, though with w (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 limit of f (R, T ) gravity models outside a spherical mass immersed in the cosmological fluid. We have found that the corresponding field equations depend on the both background values of the Ricci scalar and the background cosmological fluid density. As a result, we attain the parametrized post-Newtonian (PPN) parameter for f (R, T ) gravity and show that this theory can admit the experimentally acceptable values of this parameter. As a sample, we present the PPN gamma parameter for general minimal power law models, in particular, the model R + c1 √ −T .

Late-time cosmological approach in mimetic f(R, T) gravity

“…The main justifications for employing the trace of the energy-momentum tensor may be associated with exotic imperfect fluids or quantum effects (conformal anomaly). Different aspects of such a theory have been investigated in the literature [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. Recently, another kind of alternative gravity model has been proposed in which the metric is not considered a fundamental quantity.…”

Compact stars in $$f(R,\mathcal {T})$$ f ( R , T ) gravity

“…It has been argued that such a dependence on T may come from the presence of an imperfect fluid or quantum effects. Many cosmological applications based on f (R, T ) gravity can be found in [44][45][46][47][48][49][50][51][52][53][54][55][56][57].…”

Dynamical instability and expansion-free condition in $$f(R, T)$$ f ( R , T ) gravity

“…Here the EH action is modified in such a way that the gravitational Lagrangian includes higher order curvature terms along with the trace of the energy momentum tensor T . Shabani and Farhoudi [29] explained the weak field limit by applying a dynamical system approach and they analyzed the cosmological implications of f (R, T ) models with a variety of cosmological parameters, such as the Hubble parameter, its inverse, snap parameters, weight function, deceleration, jerk, and equation of state parameter. Ayuso et al [30] worked on a consistency criterion for a non-minimally coupled class of modified theories of gravity.…”