Mean-plaquette treatment of the mixed fundamental-adjoint SU(2) lattice gauge theory

Any statistical mean value in a lattice gauge theory without matter may be written as an integral over plaquette variables with the constraint of the Bianchi identity for each cube. A mean-plaquette approximation can thus be developed. Using this technique for a mixed fundamental-adjoint SU(2) model we reproduce all the features of the phase diagram given by Monte Carlo simulations including the existence of an end point near the crossover region on the fundamental axis.