Concentration fluctuations in binary fluid membranes.

We investigate the dynamics of critical fluctuations in binary fluid membranes using a two-dimensional hydrodynamic model with momentum decay to the surrounding water. In particular, the decay rate of concentration fluctuations is obtained analytically. In the limit of small wavenumber q with respect to the correlation length, the decay rate is proportional to q², as usual. In the large-q limit, however, the effective diffusion coefficient increases only logarithmically with q.