COHERENT AMPLIFICATION OF CLASSICAL PION FIELDS DURING THE COOLING OFDROPLETS OF QUARK PLASMA

In the framework of the linear sigma model we study the time evolution of a system of classical sigma and pion fields coupled to quarks. For this purpose we solve numerically the classical transport equation fo r relativistic quarks coupled to the nonlinear Klein-Gordon equations for the meson fields. We examine evolution starting from variety of in itial conditions corresponding to spherical droplets of hot quark matt er, which might mimic the behavior of a quark plasma produced in high- energy nucleus-nucleus collisions. For large droplets we find a strong amplification of the pion field that oscillates in time. This leads t o a coherent production of pions with a particular isospin and so woul d have similar observable effects to a disoriented chiral condensate w hich various authors have suggested might be a signal of the chiral ph ase transition. The mechanism for amplification of the pion field foun d here does not rely on this phase transition and is better thought of as a ''pion laser'' which is driven by large oscillations of the sigm a field.