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- 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) = sinh1/n(αt), where n and α are positive constants. For 0 1, the universe attains a phase transition from an early decelerating to the present accelerating phase. This model 1 starts from quintessence (ω>−1) initially and ended up with phantom phase (ω<−1) when t →∞. The second case is a(t) = (tket)1/n, where n and k are positive constants. It is observed that for n ≥ 2andk = 1, a class of transit models of the universe are obtained. The model 2 belongs to the scenario of phantom energy (ω<−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.
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- Although the standard lambda cold dark matter cosmological model is quite successful in describing the universe, there are still several issues that are still not resolved. Some of these are the cosmological constant problem, certain anomalies in the cosmic microwave background radiation and whether general relativity is valid on large scales. Therefore, it is interesting to examine modified theories in an attempt to solve these problems, and to examine the entire range of possibilities that are allowed. In this work, we examine one of these modified theories, viz., f(R,T) gravity. We study the homogeneous and isotropic models in this theory, which have some pleasing features, such as no initial singularity, a dynamic cosmological term, and a transition from early deceleration to late-time acceleration as intimated by observations. The physical parameters of the model, as well as the energy conditions, are discussed and a viable cosmological model can be constructed.
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- We consider a homogeneous and anisotropic cosmological model, namely, a Bianchi type-I model in which deceleration parameter is time dependent in the context of f (R, T ) gravity theory. To obtain exact solutions of the field equations, we use a form of the deceleration parameter that varies as the nth power of time, and covers Berman’s law (Nuovo Cimento B 74:182, 1983) where it is constant. For n =1, it covers cosmological models with linearly varying deceleration parameter given by Akarsu and Dereli (Int J Theor Phys 51:612, 2012). We extend the behavior of cosmological models for n = 2, and discuss the physical and geometrical properties of the model, and we show that the model is consistent with current observations.
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