On possible $\Theta$ vacua states in heavy ion collisions
  We have simulated the possible $\Theta$ vacua states in heavy ion collisions. In a quench like scenario, random phases of the chiral fields were evolved in a zero temperature potential incorporating the breaking of $U_A(1)$ symmetry. Initial random phases very quickly settles into oscillation around the values dictated by the potential. The simulation indicate that $\Theta$ vacua states that can be populated in heavy ion collisions is a coherent superposition of a number of modes. 
A. K. Chaudhuri