Hydrodynamics of two-dimensional smectics on fluid surfaces

The long wavelength hydrodynamics of films with unidirectional translational order adsorbed on fluid surfaces (as in a Langmuir monolayer) is formulated. We find the hydrodynamic frequencies ω(q)(± )q14/9 cos4/3θ sin14/9θ where q and π/2-θ is the angle between the direction of propagation and the direction of translational order. We also obtain the dynamic structure factor. Our results apply to nematic polymers adsorbed onto a fluid surface and to striped phases of Langmuir monolayers, and provide an experimentally accessible probe of the anomalous elasticity predicted for two-dimensional smectics by Golubović and Wang. © 1993 The American Physical Society.