Cosmic time and chaos

It is shown that the Friedman cosmological models (1) with bulk viscosity dissipation, (2) with Weyssenhoff fluid (perfect fluid with macroscopic spin), (3) with a phase transition in a very early stage of the evolution, all possessing negative space-curvature, after being compactified. exhibit chaotic behaviour in asymptotic states. Geodesic flows in such models are characterized by an exponential instability; they are mixing ergodic, and have non-zero metric entropy. In fact these world models are special cases of a "chaotic evolution" described by Lockhart, Misra and Prigogine. In particular, Prigogine’s "internal time" may be defined in them. Some remarks, concerning a predictability in cosmological models with the geodesic instability, are made.