  Ultra-relativistic nucleus-nucleus collisions create a state of matter of
high temperature and small baryo-chemical potential, which is similar to the
thermodynamical conditions in the primordial universe. Recent analyses of Au+Au
collisions at RHIC revealed the temperature, size and density of the system.
Thus, a comparison to the primordial universe can be attempted. In particular,
two observables shall be investigated, namely (1) the temperature at baryon
freeze-out (about t=10 fm/c in the $Au$ + $Au$ collision) and (2) the matter
density at the partonic stage (t>1 fm/c).
