Decelerating to accelerating scenario for Bianchi type-II string Universe in f(R,T)-gravity theory

Abstract

In this paper, we have discussed string cosmological model within the framework of [Formula: see text] theory of gravity in homogeneous but anisotropic Bianchi Type-II space-time. We have considered cosmic string as a source of energy–momentum tensor. We get the solution of the corresponding field equations by assuming deceleration parameter [Formula: see text], which is time-dependent (here, [Formula: see text] and [Formula: see text] are arbitrary constants). This particular form of scale factor enables us to explain the two scenarios, (i) By using recent constraints ([Formula: see text], [Formula: see text]) from supernovae type Ia union data (Cunha, Kinematic constraints to the transition redshift from supernovae type Ia union data, Phys. Rev. D 79 (2009) 047301), we find the values of arbitrary constants [Formula: see text] and [Formula: see text] for which we have derived a cosmological model showing accelerating expansion universe ([Formula: see text]) only throughout the evolution and (ii) By using the recent constraints ([Formula: see text], and [Formula: see text]) from SNIa data in combination with BAO and CMB observations (Giostri et al. From cosmic deceleration to acceleration: new constraints from SN Ia and BAO/CMB, J. Cosmol. Astrophys. 3 (2012) 27), we find the values of arbitrary constants for which we have derived a cosmological model with phase transition from early decelerating ([Formula: see text]) to the present accelerating ([Formula: see text]) universe. Also, for the model, we have evaluated and discussed the various physical and kinematic parameters. We have also shown the variation of these cosmological parameters graphically for specific values of the constants. The stability and physical viability are also discussed for the derived models using some recently developed diagnostic tools.