New holographic dark energy model with bulk viscosity in f(R, T) gravity

Abstract

In this paper, bulk viscosity is introduced in new holographic dark energy (HDE) to describe the effects of cosmic non-perfect fluid on the evolution of the universe in modified f (R, T ) gravity. Assuming f (R, T ) = R+λT , where R is the Ricci scalar, T , the trace of energy-momentum tensor and λ is a constant, we derive a general function of Hubble parameter with bulk viscous form to provide a procedure for the viscous new HDE model building. Especially, we assume the total bulk viscosity coefficient proportional to the velocity of the expansion of the universe in such a way that ζ = ζ 0 + ζ 1 H. We obtain the solutions of the scale factor and deceleration parameter and classify all the possible scenarios (deceleration, acceleration and their transition) with different parameter regions chosen properly for positive and negative ranges of λ, and ζ 0 and ζ 1 to analyze the evolution of the universe. It is observed that there is a transition from decelerated phase to accelerated phase at early or late time depending on the values of viscous terms. For large values of viscous terms it always accelerates through out the evolution. Furthermore, we also investigate the statefinder pair {r, s} and Om diagnostics for the viscous new HDE model to discriminate with other existing DE models. The model evolution behaviors are shown in the planes of r − s, r − q and Om − z. It is found that behavior of trajectories in different planes depend on the bulk viscous coefficient. A small combination of ζ 0 and ζ 1 gives the quintessence like behavior whereas large combination of these two terms give Chaplygin gas like model. However, both the model approaches to ΛCDM model in late time of evolution of the universe. Our viscous model is also different from other existing dark energy models. The evolution of effective equation of state parameter is -0.9745 which is very close to the observation. The entropy and generalized second law of thermodynamics are valid for this model under some constraints of bulk viscous coefficient. The analysis shows that the dark energy phenomena may be explained as the effect of bulk viscosity in the cosmic medium.

Analysis of trap distribution of a red persistent luminescent materials using thermoluminescence

“…[ 15 ] However, the use of the second‐order derivative to locate the TL peak was first illustrated by Singh. [ 16 ] The most distinct feature of a second‐order derivative is that it is easy, less time consuming, and works perfectly for highly overlapped curves.…”

Metric-Affine Myrzakulov Gravity Theories

“…[35]) theories. (In particular, assuming flatness (namely R λ µνρ = 0) and vanishing nonmetricity (83), boils down to the torsionful theories of [10,37], while demanding flatness and vanishing torsion one is left with the models of [11,12]. On the other hand, imposing only teleparallelism in (83) we are left with the generalized theories of [38,39].)…”

“…(In particular, assuming flatness (namely R λ µνρ = 0) and vanishing nonmetricity (83), boils down to the torsionful theories of [10,37], while demanding flatness and vanishing torsion one is left with the models of [11,12]. On the other hand, imposing only teleparallelism in (83) we are left with the generalized theories of [38,39].) The MG-VIII model is the most general of the MG theories, the function F = F(R, T, Q, T ) in (83) being a generic function of the scalar curvature R of the general affine connection Γ λ µν , the torsion scalar T, the nonmetricity scalar Q, and the energy-momentum trace T .…”

“…These could be physically significant to discuss early stages of the evolution of the universe. Moreover, a new holographic dark energy model with bulk viscosity in F(R, T ) gravity has been recently proposed in [83] (the model considered there approaches the ΛCDM one in the late-time evolution of the universe). Furthermore, in [84] a bulk viscous cosmological model in F(R, T ) gravity was considered.…”