Cluster variation method, Padé approximants, and critical behavior

In the present paper we show how nonclassical, quite accurate, critical exponents can be extracted in a very simple way from the Padé analysis of the results obtained by mean-field-like approximation schemes, and in particular by the cluster variation method. We study the critical behavior of the Ising model on several lattices (quadratic, triangular, simple cubic and face centered cubic) and two problems of surface critical behavior. Both unbiased and biased approximants are used, and results are in very good agreement with the exact or numerical ones.