Journal of Statistical Physics, Vol. 66, Nos. 3/4, 1992. p. 897-911.
An improved version of a cluster-effective-field theory for spin glasses, namely the double-cluster approximation, is formulated. The present version is based not on the self-consistency condition, but on the double-cluster-consistency condition. The advantages of the approximation combined with the coherent-anomaly method are discussed. The critical data of the spin-glass susceptibility are estimated for the two-, three-, and four-dimensional +_J models.