Nonlinear renormalization of the surface-order-parameter interface Hamiltonian

The coupling between order-parameter fluctuations near the wall and depinning fluid interface in the approach to a complete wetting transition is described by a two-field Hamiltonian H-2[l(1),l(2) which improves upon standard capillary-wave models of wetting. We construct a nonlinear renormalization group to study fluctuation effects in d = 3 and show how this elegantly rederives the expression for the renormalized wetting parameter found in earlier (linear) renormalization-group treatments.