EFFECTIVE-FIELD RENORMALIZATION-GROUP APPROACH FOR ISING LATTICE SPINSYSTEMS

A new applicable real-space renormalization group framework (EFRG) for computing the critical properties of Ising lattice spin systems is pr esented. The method, which follows up the same strategy of the mean-fi eld renormalization group scheme (MFRG), is based on rigorous Ising sp in identities and utilizes a convenient differential operator expansio n technique. Within this scheme, in contrast with the usual mean-field type of equation of state, all the relevant self-spin correlations ar e taken exactly into account. The results for the critical coupling an d the critical exponent nu, for the correlation length, are very satis factory and it is shown that this technique leads to rather accurate r esults which represent a remarkable improvement on those obtained from the standard MFRG method. In particular, it is shown that the present EFRG approach correctly distinguishes the geometry of the lattice str ucture even when employing its simplest size-cluster version. Owing to its simplicity we also comment on the wide applicability of the prese nt method to problems in crystalline and disordered Ising spin systems .