Cluster variation method and disorder varieties of two–dimensional Ising–like models
نویسنده
چکیده
I show that the cluster variation method, long used as a powerful hierarchy of approximations for discrete (Ising-like) two-dimensional lattice models, yields exact results on the disorder varieties which appear when competitive interactions are put into these models. I consider, as an example, the plaquette approximation of the cluster variation method for the square lattice Ising model with nearest-neighbor, next-nearest-neighbor and plaquette interactions, and, after rederiving known results, report simple closed-form expressions for the pair and plaquette correlation functions. PACS numbers: 05.50.+q, 64.60.Cn, 75.10.Hk Typeset using REVTEX
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