The Correlation Length and the Critical Exponent u; through the Simplified Cluster Variation Method and the Coherent Anomaly Method

Abstract

The correlation length of the Ising model on the simple cubic lattice is calculated directly from the magnetization profiles which are determined in the pair, the square, and the cube approximations in the simplified cluster variation method. The critical exponent ν is obtainedby applying the coherent anomaly method to the correlation length.The wave-number dependent magnetic susceptibility or the spin-pair correlation function is not required in obtainingthe expression for the correlation length.