Correlation theory of fluctuations of the surface of a transparent liquid in the field of strong optical radiation

A co-relation theory is given of fluctuations of the surface of a transparent liquid of arbitrary viscosity in the presence of strong optical radiation. It is shown that an analysis based on the well-known Onsager hypothesis gives an expression for the spectral density of fluctuations of the surface which is different from that obtained by introducing external fluctuation forces and assuming that the strength of these forces is governed by the equilibrium fluctuation-dissipation theorem. The theory is generalized to a superfluid liquid.