ON THE STIFFNESS OF AN INTERFACE NEAR A WALL

The relevance of the bare stiffness, SIGMA(l), of an interface at dist ance l from a planar wall, for the renormalization-group theory of cri tical-wetting instabilities in short-range, (d = 3)-dimensional system s is briefly recalled. A careful derivation is presented of an express ion for SIGMA(l) at the van der Waals/mean field level in terms of the order-parameter profile m(PI) (z, l) of a planar interface. The analy sis completes and improves the treatment of Jin and Fisher [Phys. Rev. B 47, 7365 (1993)].