LONG-RANGE COULOMB INTERACTION AND PHASON PROPAGATOR IN CHARGE-DENSITY-WAVE

Within mean field theory we reexamine the collective modes associated with the phase fluctuation in the presence of long range Coulomb inter action. We find that the phason propagator is dominated by an acoustic mode and an optical mode. These modes have already been described by Nakane and Takada and Wong and Takada. However, due to their inconsist ent approximations, their results became unreliable; particularly in t he vicinity of the transition temperature. Relevance of these modes to those found in the Raman and neutron scattering from blue bronze is b riefly discussed.