PHASON DYNAMICS IN SPIN-DENSITY WAVES

We study the phason propagator and the electric conductivity of spin d ensity waves (SDW) in the presence of long range Coulomb interaction. We find that in the longitudinal limit, the phason propagator is stron gly modified, while in the transverse limit, the Coulomb effect disapp ears completely. Further in the longitudinal limit, the plasmon exhaus ts the optical sum rule independent of whether the system is in the no rmal state or in SDW. However, in the transverse limit, the plasmon co ntribution drops out completely from the conductivity. On the other ha nd, the polariton will give rise to a peculiar structure in the low fr equency absorption.