Bianchi-I massive string cosmological models in general relativity

Abstract—In present paper, we study some massive string cosmological models in a homogeneous and anisotropic Bianchi-I space-time. To get the deterministic solutions of Einstein’s field equations, we assume that the expansion scalar in the models is proportional to one of the components of shear tensor and the scale factor a = (tket) 1 n which yields a time-dependent deceleration parameter. It is observed that for n ≤ 1, the models are not physically feasible whereas for n ≥ 1, we can generate a class of physically viable models. It is also detected that the models of the universe have a transition from early decelerated phase to the recent accelerating phase at present epoch which is consistent with recent astrophysical observations. The study reveals that massive strings dominate in the early universe. The strings eventually disappear from the universe for sufficiently large times, which is in agreement with current astronomical observations. Some physical and geometric aspects of the models are also discussed. Index Terms—String, Bianchi type I universe, Variable deceleration parameter, Accelerating universe I