Critical Slowing Down near Chiral Phase Transition

The hydrodynamic model provides a powerful tool to describe dynamics in heavy-ion collisions. However, it will be inadequate to describe nonequilibrium phenomena near the QCD phase transition.Because it is valid only in the case where we are interested in gross variables associated with macroscopic scales and they must be widely separated from microscopic variables. Thissimple picture loses its validity near the critical points because of the indefinitely increase of the correlation length. Then,the critical dynamics can be described by the Langevin equation.In this study, we derive a linear Langevin equation in the Nambu-Jona-Lasinio model in the chiral limit. By using the Langevin equation, we discuss the critical dynamics of the chiral phase transition.Then, we show that the critical slowing down in the chiral phasetransition is enhanced in large chemical potential region and around the tricritical point.