Narrow Results

In this paper, we have researched tachyon field, k-essence and quintessence dark energy (DE) models for Friedmann–Robertson–Walker (FRW) universe with varying G and $\mathrm{\Lambda }$ in f(R, T) gravitation theory. The theory of f(R, T) is proposed by Harko et al. [Phys. Rev. D84, 024020, 2011]. In this theory, R is the Ricci scalar and T is the trace of energy–momentum tensor. For the solutions of field equations, we have used linearly varying deceleration parameter (LVDP), the equation of state (EoS) and the ratio between $\mathrm{\Lambda }$ and Hubble parameter. Also, we have discussed some physical behavior of the models with various graphics.

In this work, LRS Bianchi type-I cosmological model with perfect fluid source in $f(R,T)$ gravity theory, where $R$ is the Ricci scalar and $T$ is the trace of the stress energy-momentum tensor, has been studied in order to investigate early time deceleration and late time acceleration of the universe. By proposing a new special form of time-varying deceleration parameter in terms of Hubble parameter, the exact solution of the field equations has been obtained. The physical and geometric quantities of the model have been derived and their evolution has been discussed. Our model has an initial singularity and initially exhibits decelerating expansion and transits to accelerating expansion phase at last eras. The nature of the matter source of the model is consistent with the standard model in frame of the structure formation.

A non-minimally coupled cosmological model is studied in $f(R,T)=f_1(R)+f_2(R)f_3(T)$ gravity for a particular choice of the function in the background of flat Friedmann–Robertson–Walker universe. The modified field equations are solved with the help of a varying deceleration parameter. The time evolution of the model is analyzed for both the dynamic and kinematic quantities. For testing the viability of the results, energy conditions and the statefinder diagnostic are used. It has been shown that this model, which we discussed to examine the phase transition in the expansion of the universe, is compatible with current astrophysical observations, and that the DE model dominating the early universe is Chaplygin gas, while the model dominating the late universe is quintessence.