Filling transition for a wedge.

We study the formation and the shape of a liquid meniscus in a wedge with opening angle 2phi which is exposed to a vapor phase. By applying a suitable effective interface model, at liquid-vapor coexistence and at a temperature Tphi we find a filling transition at which the height of the meniscus becomes macroscopically large while the planar walls of the wedge far away from its center remain nonwet up to the wetting transition occurring at Tw>Tphi. Depending on the fluid and the substrate potential the filling transition can be either continuous or discontinuous. In the latter case it is accompanied by a prefilling line extending into the vapor phase of the bulk phase diagram and describing a transition from a small to a large, but finite, meniscus height. The filling and the prefilling transitions correspond to nonanalyticities in the surface and line contributions to the free energy of the fluid, respectively.