On the stiffness of an interface near a wall

The relevance of the bare stiffness, ( l ), of an interface at distance l from a planar wall, for the renormalization‐group theory of critical‐wetting instabilities in short‐range, ( d = 3)‐dimensional systems is briefly recalled. A careful derivation is presented of an expression for ( l ) at the van der Waals/mean field level in terms of the order‐parameter profile m ∏ ( z, l ) of a planar interface. The analysis completes and improves the treatment of Jin and Fisher [Phys. Rev. B 47 , 7365 (1993)].