Dynamical evolution of the scalar condensate in heavy ion collisions - art. no. 054901

We derive the effective coarse-grained field equation for the scalar conden sate of the linens sigma model in a simple and straightforward manner using linear response theory. The dissipative coefficient is calculated consiste ntly at tree level on the basis of the physical processes of sigma-meson de cay and of thermal sigma mesons and pions knocking sigma mesons out of the condensate. The field equation is solved for hot matter undergoing either o ne- or three-dimensional expansion and cooling in the aftermath of a high e nergy nuclear collision. The results show that the time constant far return ing the scaler condensate to thermal equilibrium is of order 2 fm/c.