Some effects of long range forces on interfacial phenomena

The conventional theory of interfaces (with a free energy term ∼ (∇ρ) 2 where p is the appropriate density) may be qualitatively incorrect, because of long range effects associated with Van der Waals forces. 1) The tail of the density profile on the gas side of a liquid gas interface is not exponential (as usually predicted) but is ∼ z-3 (where z is the distance from the midpoint). 2) In the Moldover Cahn experiment, the thickness of the wetting layer of a liquid (b) between two other liquids (a) and (c) can be controlled by long range forces, not by the exponential repulsion between two interfaces which is derived from the conventional theory.