Thermalization of the quark-gluon plasma and Bose-Einstein condensation in unusual circumstances

There is robust evidence from RHIC, and now from the LHC, that matter
produced in ultra-relativistic heavy ion collisions is (nearly) in
local equilibrium. To understand how this is achieved, that is, to
understand the detailed mechanisms by which the partonic degrees of
freedom of the initial nuclear wave functions get freed and
subsequently interact to reach local equilibrium, is a challenging
problem.

In this talk, I shall focus on a particular phenomenon that could play
a role in the process of thermalization, namely the strong
amplification of very soft gluon modes, possibly leading to the
formation of a transient Bose-Einstein condensate. Aside from its
potential relevance to the thermalization problem, the formation of
such a condensate in relativistic systems is an interesting problem in
itself. I shall report on a recent study of the onset of condensation
in hot gluon systems using kinetic theory in the approximation of
small scattering angles. The scaling regime that develops near the
onset of condensation will be discussed. Comparison with similar
phenomena in other systems (early universe cosmology, cold atom
systems) will be also briefly presented.