Two-fluid atmosphere from decelerating to accelerating Friedmann-Robertson-Walker dark energy models

Evolution of dark energy parameter within scope of a spatially homogeneous and isotropic Friedmann-Robertson-Walker model filled with perfect fluid and dark energy components is studied by generalizing recent results. The two sources are claimed to interact minimally so that their energy momentum tensors are conserved separately. The conception of time-dependent deceleration parameter with some suitable assumption yields an average scale factor , with alpha and n being positive arbitrary constants. For 0 < n a parts per thousand currency sign 1, this generates a class of accelerating models while for n > 1, the models of universe exhibit phase transition from early decelerating phase to present accelerating phase which is supported by results from recent astrophysical observations. It is observed that the transition red shift (z (t) ) for our derived model with q (0) = -0.73 is a parts per thousand...0.32. This is in good agreement with cosmological observations in literature. Some physical and geometric properties of this model along with physical acceptability of cosmological solutions have been discussed in detail.