Constraint Correlation Dynamics of SU(N) Gauge Theories
  A constraint correlation dynamics up to 4-point Green functions is proposed for SU(N) gauge theories which reduces the N-body quantum field problem to the two-body level. The resulting set of nonlinear coupled equations fulfills all conservation laws including fermion number, linear and angular momenta as well as the total energy. Apart from the conservation laws in the space-time degrees of freedom the Gauss law is conserved as a quantum expectation value identically for all times. The same holds for the Ward identities as generated by commutators of Gauss operators. The constraint dynamical equations are highly non-perturbative and thus applicable also in the strong coupling regime, as e.g. low-energy QCD problems. 
S.J. Wang, W. Cassing, J.M. Haeuser, A. Peter, M.H. Thoma