The problem of quantization of lightcone QCD
  There exists the problem to construct a quantum algebra of observables in lightcone QCD beyond the perturbative regime. It has recently established that the boundary gauge fields are crucial for a consistent construction of the classical dynamic system. If the gauge group is non-Abelian and there are four or more space-time dimensions then the procedure of symplectic reduction gives a classical dynamical system with very complicated Hamiltonian having infinite power over the coupling constant. Then, to quantize the theory one should to construct a Poisson algebra and to quantize it. Careful analysis shows that a Poisson formulation has a problem with: canonical commutation relations, spatial invariance, and the boundary degrees of freedom in the Hamiltonian. 
Alexey V. Popov
hep-ph hep-th