Multieffectivefield theory: Applications to the CAM analysis of the twodimensional Ising model
Abstract
A multieffectivefield theory is formulated and applied to the twodimensional Ising model from the viewpoint of the coherentanomaly method (CAM). Two necessary conditions to construct the CAM canonical series are shown. Two series of approximations are derived on 3×3 and 4×4clusters and with the use of the CAM we estimate the critical exponent of the susceptibility within an error of 0.37 and 0.45 percent, respectively, for the exact value γ = 1.75 where the exact T_{c} is assumed. This accuracy of the estimation shows the effectiveness of this theory. It is generally proved that certain kinds of approximations with different combinations of effective fields yield exactly the same approximate critical temperature and meanfield coefficient.
 Publication:

Physica A Statistical Mechanics and its Applications
 Pub Date:
 June 1991
 DOI:
 10.1016/03784371(91)90344C
 Bibcode:
 1991PhyA..174..479M