  The realistic equation of state of strongly interacting matter, that has been
successfully applied in the recent hydrodynamic studies of hadron production in
relativistic heavy-ion collisions at RHIC, is used in the Friedmann equation to
determine the precise time evolution of thermodynamic parameters in the early
Universe. A comparison with the results obtained with simple ideal-gas
equations of state is made. The realistic equation of state describes a
crossover rather than the first-order phase transition between the quark-gluon
plasma and hadronic matter. Our numerical calculations show that small
inhomogeneities of strongly interacting matter in the early Universe are
moderately damped during such crossover.
