Phase diagram of the Z(5) model on a square lattice

Abstract
A general five-state model, which contains the five-state Potts model and a solid-on-solid model as special cases, is studied. The authors find that the high-temperature paramagnetic and the low-temperature ordered phases are separated either by a line of first-order transitions or by an intermediate phase with algebraic decay of correlations. The phase diagram is proposed on the basis of general considerations and Monte-Carlo simulations.