Surface Free Energies and Surface Critical Behaviour of the ABF Models with Fixed Boundaries

Abstract

In a previous paper, we introduced reflection equations for interaction-round-a-face (IRF) models and used these to construct commuting double-row transfer matrices for solvable lattice spin models with fixed boundary conditions. In particular, for the Andrews-Baxter-Forrester (ABF) models, we derived special functional equations satisfied by the eigenvalues of the commuting double-row transfer matrices. Here we introduce a generalized inversion relation method to solve these functional equations for the surface free energies. Although the surface free energies depend on the boundary spins we find that the associated surface critical exponent $\alpha_s=(7-L)/4$ is independent of the choice of boundary.