ARE STEADILY MOVING CRYSTALS UNSTABLE

We study the dynamics of small fluctuations about the uniform state of a crystal moving through a dissipative medium, e.g., a sedimenting co lloidal crystal or a moving flux lattice, using a set of continuum equ ations for the displacement fields, and a one-dimensional driven latti ce-gas model for the coupled concentration and tilt fields. For the co lloidal crystal we predict a-continuous nonequilibrium phase transitio n to a clumped state above a critical Peclet number.