Disoriented chiral condensate formation from a state with collective pion fields

At high temperatures it is believed that one can create a highly excited state, the starting point of disoriented chiral condensate (DCC) formation, which is sitting at the top of a potential barrier. We study here instead the evolution of a state where energy is stored initially in the collective motion too, in particular, in chiral rotations representing collective pion fields. We simulate the creation of such an initial state by letting the hot system evolve in time without cooling. It covers the microcanonically allowed phase space if the classical dynamics of the system is chaotic. We find the collective field dynamics chaotic in the linear σ model coupled to quarks with explicit symmetry breaking. A rapid linear expansion from such initial states leads eventually to DCC formation. copyright 1997 The American Physical Society