Dynamic Long-Range Forces andZBranches at Phase Transitions

Abstract

We show that the critical dynamics of dense pseudospin systems interacting via retarded long-range forces (e.g., acoustic phonons) gives rise to the appearance of a $Z$ branch in the central-peak dispersion which should be observable by light-scattering techniques. The evolution of an initially nonconserved quantity towards a hydrodynamic regime leads to liquidlike behavior of the solid for a range of wave vectors.