Quality of the mean-field approximation: A low-order generalization yielding realistic critical indices for three-dimensional Ising-class systems

Modification of the renormalization-group approach, invoking Stratonovich transformation at each step, is proposed to describe phase transitions in three-dimensional Ising-class systems. The proposed method is closely related to the mean-field approximation. The low-order scheme that works well for a wide thermal range is consistent with a scaling hypothesis and predicts very reasonable values of critical indices.