INTERFACES IN THE POTTS-MODEL .2. ANTONOV RULE AND RIGIDITY OF THE ORDER-DISORDER INTERFACE

Within the ferromagnetic q-state Potts model we discuss the wetting of the interface between two ordered phases a and b by the disordered phase f at the transition temperature. In two or more dimensions and for q large we establish the validity of the Antonov's rule, sigma-ab = sigma-af + sigma-fb, where sigma denotes the surface tension between the considered phases. We also prove that at this temperature, in three or more dimensions the interface between any ordered phase and the disordered one is rigid.