Dissipation, noise and DCC domain formation

The possibility of forming disoriented chiral condensate (DCC) in relativistic heavy ion collisions has generated considerable research activities in recent years. The idea was first proposed by Rajagopal and Wilczek [1–4]. They argued that for a second order chiral phase transition, the chiral condensate can become temporarily disoriented in the nonequilibrium conditions encountered in heavy ion collisions. As the temperature drops below Tc, the chiral symmetry begins to break by developing domains in which the chiral field is misaligned from its true vacuum value. The misaligned condensate has the same quark content and quantum numbers as do pions and essentially constitute a classical pion field. The system will finally relaxes to the true vacuum and in the process can emit coherent pions. Since the disoriented domains have well defined isospin orientation, the associated pions can exhibit novel centauro-like [5–8] fluctuations of neutral and charged pions [9–12]. Most dynamical studies of DCC have been based on the linear sigma model, in which the chiral degrees of freedom are described by the real O(4) field Φ = (σ,Π → ), having the equation of motion,