Amplification of pionic instabilities in high-energy collisions?
  Considering a variety of dynamical scenarios within the linear sigma model, we examine the conditions for pionic modes to be amplified as the chiral field relaxes towards the normal vacuum following the transient restoration of approximate chiral symmetry in a high-energy collision. While Bjorken-type longitudinal expansions appear to be insufficient for amplification for occur, analoguos expansions in two or three dimensions may enhance the low-energy power spectrum by up to an order of magnitude. 
J. Randrup (Lawrence Berkeley Laboratory, Berkeley, USA)