Equations of state of the Potts ferromagnet in an anisotropic square lattice: Renormalization-group approach

Abstract

We extend to the anisotropic case (not necessarily equal coupling constants along the various crystalline directions) the real-space renormalization-group procedure recently introduced by Caride and Tsallis, which directly yields the order parameter for arbitrary temperatures. The method does not demand the calculation of the thermodynamic energy; it is as simple as a mean-field calculation although it provides nontrivial results, which can be systematically improved. We apply the procedure to the q-state Potts ferromagnet in an anisotropic square lattice, whose exact equation of state is still unknown. The results compare satisfactorily with available exact results.