EFFECTIVE ACTIONS FOR FINITE-TEMPERATURE LATTICE GAUGE-THEORIES

We consider a lattice gauge theory at finite temperature in (d + 1) di mensions with the Wilson action and different couplings beta(t) and be ta(s) for timelike and spacelike plaquettes. By using the character ex pansion and Schwinger Dyson type equations we construct, order by orde r in beta(s), an effective action for the Polyakov loops which is exac t to all orders in beta(t). As an example we construct the first non-t rivial order in beta(s) for the (3+1) dimensional SU(2)model and use t his effective action to extract the deconfinement temperature of the m odel.