  Strongly correlated systems far from equilibrium can exhibit scaling
solutions with a dynamically generated weak coupling. We show this by
investigating isolated systems described by relativistic quantum field theories
for initial conditions leading to nonequilibrium instabilities, such as
parametric resonance or spinodal decomposition. The non-thermal fixed points
prevent fast thermalization if classical-statistical fluctuations dominate over
quantum fluctuations. We comment on the possible significance of these results
for the heating of the early universe after inflation and the question of fast
thermalization in heavy-ion collision experiments.
