Long-ranged surface perturbations for confined fluids

When a fluid, or magnet, is confined between parallel walls that exert opposing surface fields h₂=-h₁ the order-parameter (magnetization) profile near one wall can be modified severely by the presence of the other. For sufficiently low dimensions (d3) the surface-layer perturbation and the force between the walls decay algebraically with wall separation L for all temperatures Tc,b{≥}T{≥}Tw. Near Tw, the temperature of a critical wetting transition, the perturbation can be longer ranged than at the bulk critical temperature Tc,b. The predictions of a scaling theory are supported, for d=2, by results obtained from interfacial Hamiltonians and from Monte Carlo simulations of the Ising strip.