A cosmological model with a specific form of the Hubble parameter is constructed in a flat homogeneous, and isotropic background in the framework of f (R, T ) gravity, where R is the scalar curvature and T is the trace of the stress-energy-momentum tensor. The proposed functional form of the Hubble parameter is taken in such a way that it fulfills the successful bouncing criteria to find the solution of the gravitational field equations provided the Universe is free from initial singularity. The various constraints on the parameters are involved in the functional form of the Hubble parameter which is analyzed in detail. In addition, we explore physical and geometrical consequences of the model based on the imposed constraints. Furthermore, we demonstrate the bouncing scenario which are realized in our model with some particular values of the model parameters. As a result, we find that all of the necessary conditions are satisfied for a successful bouncing model.

In this paper, we propose a simple parametrization of the Hubble parameter H in order to explain the late time cosmic acceleration. We show that our proposal covers many models obtained in different schemes of parametrization under one umbrella. We demonstrate that a simple modification in the functional form of Hubble parameter can give rise to interesting cosmological phenomena such as big rip singularity, bounce and others. We have also constrained the model parameters using the latest 28 points of H(z) data for three cases which admit transition from deceleration to acceleration.Comment: 24 pages, 5 figure

The paper presents late time cosmology in f (Q, T) gravity where the dark energy is purely geometric in nature. We start by employing a well motivated f (Q, T) gravity model, f (Q, T) = mQ n + bT where m, n and b are model parameters. Additionally we also assume the universe to be dominated by pressure-less matter which yields a power law type scale factor of the form a(t) = c2(At + c1) 1 A , where A = 3(8π + b) n(16π + 3b) and c1 & c2 are just integration constants. To investigate the cosmological viability of the model, constraints on the model parameters were imposed from the updated 57 points of Hubble data sets and 580 points of union 2.1 compilation supernovae data sets. We have thoroughly investigated the nature of geometrical dark energy mimicked by the parametrization of f (Q, T) = mQ n + bT with the assistance of statefinder diagnostic in {s, r} and {q, r} planes and also performed the Om-diagnostic analysis. The present analysis makes it clear-cut that f (Q, T) gravity can be promising in addressing the current cosmic acceleration and therefore a suitable alternative to the dark energy problem. Further studies in other cosmological areas are therefore encouraging to further investigate the viability of f (Q, T) gravity.

In this article, we have investigated the role of bulk viscosity to study the accelerated expansion of the universe in the framework of modified f (Q) gravity. The gravitational action in this modified gravity theory has the form f (Q), where Q denote the non-metricity scalar. In the present manuscript, we have considered a bulk viscous matter-dominated cosmological model with the bulk viscosity co-H + H which is proportional to the velocity and acceleration of the expanding universe. Two sets of limiting conditions on the bulk viscous parameters ξ 0 , ξ 1 , ξ 2 and model parameter α arose here out of which one condition favours the present scenario of cosmic acceleration with a phase transition and corresponds to the universe with a Big Bang origin. Moreover, we have discussed the cosmological behaviour of some geometrical parameters. Then, we have obtained the best fitting values of the model parameters ξ 0 , ξ 1 , ξ 2 and α by constraining our model with updated Hubble datasets consisting of 57 data points and recently released Pantheon datasets consisting of 1048 data points which show that our obtained model has good compatibility with observations. Further, we have also included the Baryon Acoustic Oscillation (BAO) datasets of six data points with the Hubble & Pantheon datasets and obtained slightly different values of the model parameters. Finally, we have analyzed our model with the statefinder diagnostic analysis and found some interesting results and are discussed in details.

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