Equilibrium criterion and effective spin models for finite temperature   gauge theories
  Using the example of the SU(2) gauge theory in 3+1 dimensions we consider the construction of a 3-dimensional effective model in terms of Polyakov loops. We demonstrate the application of an equilibrium self-consistency condition to the systematic analysis of the contribution of various (global Z(2) symmetric) terms in the effective model action. We apply this analysis to the construction of a simple effective action with the minimum necessary number of operators. Such an action is shown to be capable of reproducing relevant observables, e.g. the Polyakov loop ensemble average, within the desired accuracy. 
Alexander Velytsky