  The expanding fireball shortly after a heavy ion collision may be
qualitatively described by a condensate of color fields or gluons which is
analogous to Bose-Einstein-condensation for massive bosonic particles. This
condensate is a transient non-equilibrium phenomenon and breaks Lorentz-boost
symmetry. The dynamics of color field condensates involves collective
excitations and is rather different from the perturbative scattering of gluons.
In particular, it provides for an efficient mechanism to render the local
pressure approximately isotropic after a short time of 0.2 fm/c. We suggest
that an isotropic color field condensate may play a central role for a simple
description of prethermalization and isotropization in the early stages of the
collision.
