Structure and tension of interfaces

This is an informal review of some of the ideas, both historical and current, in the theory of interfacial structure and tension. After recalling briefly the van der Waals theory of the late 19th century, and noting the analogy between the equations in the simplest version of that theory and those in the classical dynamics of a particle, the account goes on to consider more recent elaborations and applications of the central ideas. These include applications to three-phase equilibria, wetting and pre-wetting, line and boundary tension, and fluctuations in the structures of interfaces and three-phase lines. In the study of fluctuations there is an analogy to quantum mechanics and the Schrödinger equation, just as there is an analogy to classical mechanics in the theory of equilibrium average structures.