Transit dark energy string cosmological models with perfect fluid in F(R, T)-gravity

In this paper, spatially homogeneous and anisotropic Bianchi type-VI0 dark energy (DE) cosmological transit models with string fluid source in f(R, T) gravity [T. Harko et al., Phys. Rev. D 84 (2011) 024020], where R is the Ricci scalar and T the trace of the stress energy-momentum tensor, have been studied in the context of early time decelerating and late-time accelerating expansion of the Universe as suggested by the recent observations. The exact solutions of the field equations are obtained first by using generalized hybrid expansion law (HEL) a = (t(alpha)epsilon(ss t))(1/n) which yields a time-dependent deceleration parameter q = -1 + alpha n/(alpha+ss t)(2) and second by considering the metric coefficient A = a(k) . By using recent constraints from supernovae type-Ia union data [Cunha, arXiv: 0811.2379[astro-ph]], we obtain alpha = 0.8 and ss = 0.1184 for transit model n = 2. The Universe has an initial singularity and is anisotropic closed and it tends to be flat at the late time, i.e. our Universe is in accelerating expansion. Our model shows a phase transition property from decelerating to accelerating. It is remarkable to mention here that our Universe is homogeneous and anisotropic in the early phase whereas it becomes homogeneous and isotropic for k = 1. We have also discussed the stability of the background solution with respect to perturbations of the metric along with the properties of future singularities in the Universe dominated by DE including the phantom-type fluid. Various physical and dynamical parameters are also calculated and investigated in terms of time and redshift both.