Critical line of symmetry restoration in lattice SU(2) QCD

We study the restoration of global symmetries of lattice QCD at finite temperature and chemical potential. The hamiltonian of lattice SU(Nc) QCD in the A0 = 0 gauge has to be supplemented by the Gauss law constraint, that thermal excitations must satisfy. We examine this problem in the strong coupling limit at fixed Nc = 2. The free energy to be minimized must be defined by traces over states restricted to be local color singlets. To compute these traces one can make use of the orthogonality relations of the characters of the gauge group, a simple problem in the case of SU(2). We find the critical curve in the T-μ plane beyond which there is restoration of the global symmetry of the system, the dynamical fermion mass becoming zero. We find, for one flavor, T c = 2m 0 3 (μ=0); μ c =m 0 (T=0) (m 0 = quark dynamical mass at zero temperature ) . Relatively to an unconstrained free energy, the effect of the Gauss law is to increase the critical temperature, as the effective number of thermally excited degrees of freedom has decreased.