Accelerating bulk viscous LRS Bianchi-II string cosmological models in S ́aez-Ballester theory of gravitation

Abstract

In this paper, we obtain a spatially homogeneous and anisotropic Locally Rotationally Symmetric Bianchi type-II string cosmological model of the universe for bulk viscous fluid distribution within the framework of scalar-tensor theory of gravitation proposed by S´aez and Ballester (Phys. Lett. 113:467, 1986). To prevail the deterministic solutions we consider time-dependent deceleration parameter (DP) which provides the value of scale factor as a = [sinh(αt)] 1 n , where α and n are arbitrary positive constants. This acclimates time-dependent DP representing models which generate a transition of the universe from the early decelerated phase to the recent accelerating phase. It is also observed that for 0 less than n less or equal than 1, our model is in accelerating phase but for n greator than 1, our model is evolving from decelerating phase to accelerating phase. The modified Einstein’s field equations are solved exactly and the derived model is found to be in good concordance with recent observations. Some physical and geometric properties of the models are also discussed.