Abstract

The present study has been conducted in the framework of Brans-Dicke theory, using FRW metric with flat space, to determine the time dependence of the Brans-Dicke parameter, energy density and the equation of state parameter of the cosmic fluid in an universe expanding with acceleration, following a phase of decelerated expansion. For this purpose, a scale factor has been so chosen that the deceleration parameter, obtained from it, changes its sign from positive to negative as time goes on. Considering the total pressure to be due to the entity named dark energy, the time dependence of energy parameters for matter and dark energy have been determined. Time dependence of the equation of state parameter for dark energy has also been studied. Time variations of all these parameters have been shown graphically. It is quite evident from the present study that the dependence of the scalar field upon the scale factor plays a very important role in governing the time evolution of the cosmological quantities mentioned above. This model has an inherent simplicity in the sense that it allows one to determine the time evolution of dark energy without involving any self interaction potential or cosmological constant in the formulation.