Hydrodynamic fluctuations of spherical micelles and vesicles

Low-frequency collective excitations of spherical vesicles and microemulsion droplets (micelles) are considered. The fluid droplets are coated with a thin film and immersed in a fluid with different properties. The compressibility of the bulk fluids is taken into account. The thermal fluctuations of the system are studied within the hydrodynamic correlation theory. The method of analysis comprises a solution of the linearized hydrodynamic (Navier-Stokes and continuity) equations with random stresses and application of the fluctuation-dissipation theorem. The spectral densities of correlation functions are obtained for both the hydrodynamic fluctuations of the bulk fluids and the fluctuations excited by the surface random sources. A number of special cases of the shape fluctuations of micelles and capillary excitations of vesicles are considered.