Unified description of the early universe

A homogeneous and isotropic cosmological model of the universe is studied in which the parameter gamma of the ''gamma-law'' equation of state p = (gamma - 1)rho varies continuously with cosmological time. A unified description of the early evolution of the universe is given in which an inflationary period is followed by a radiation dominated phase. Comparing the dynamics of the model with those models endowed with matter creation or vacuum energy decay, allows us to establish the time dependence of the creation rate and of the cosmological constant in terms of the varying gamma index.