LRS Bianchi type-I cosmological models with accelerated expansion in f(R, T) gravity in the presence of $\Lambda$(T)

Abstract

This paper examines the physical behaviour of the transition of the LRS Bianchi type-I perfect-fluid cosmological models from early decelerating to the current accelerating phase within the framework of the f(R,T) theory of gravity. To determine the solution of the field equations, the concept of a time-dependent deceleration parameter is used. This yields scale factors for which the universe attains a phase transition scenario, and is consistent with recent cosmological observations. Two cases are considered, firstly $a(t) = \sinh^{1/n} (\alpha t)$ , where n and $\alpha$ are positive constants. For $0 < n\leq 1$ , this generates a class of accelerating models, while for $n > 1$ , the universe attains a phase transition from an early decelerating to the present accelerating phase. This model 1 starts from quintessence ( $\omega > - 1$ ) initially and ended up with phantom phase $(\omega < - 1)$ when $t \rightarrow \infty$ . The second case is $a(t) = (t^{k} e^{t})^{1/n}$ , where n and k are positive constants. It is observed that for $n \geq 2$ and $k = 1$ , a class of transit models of the universe are obtained. The model 2 belongs to the scenario of phantom energy ( $ \omega > - 1$ ). We have observed the existence of type-III singularity in our model 2. Some physical and geometric properties of the models are found and discussed.