FLUCTUATING FLUID INTERFACES

The thermal motion of an interface between two immiscible fluids and its coupling to spontaneous fluctuations in the bulk are studied. Theoretical analysis and simulation of a momentum-conserving lattice gas shows that an initially flat interface roughens in a manner that satisfies a dynamical scaling law. The equilibrium correlations of the interface height are derived theoretically from a fluctuation-dissipation theorem. Both the correlations and the roughening of the simulated interface are found to be in good agreement with theory over a remarkably large range of length and time scales. © 1995 The American Physical Society.