Is short-range ‘‘critical’’ wetting a first-order transition?

Current renormalization-group theory for critical wetting with short-range forces uses the interfacial Hamiltonian Fdy[1/2Σ${\mathrm{̃}}_{\mathrm{\infty }}$(∇l${)}^2$+W(l)] for the wall-interface separation l(y) (≫${\xi }_{\mathrm{\beta }}$, the bulk correlation length). For d=3 dimensions it has predicted strong nonuniversal singularities that are inconsistent with simulations. But we show that a variable interfacial stiffness, Σ${\mathrm{̃}}_{\mathrm{\infty }}$+ΔΣ̃(l), arises and must also be allowed for. The sign and ${\mathit{le}}_{\mathrm{\beta }}^{\mathrm{-}2\mathit{l}/\xi }$ decay of Σ̃(l) near the transition leads, for typical parameter values, to a fluctuation-induced, first-order wetting transition which may explain the simulation.