Notes:
The solutions of the theory must exhibit 2 “properties” observed in Nature (but not in the Lagrangian):
Confinement: quarks and gluons do not exist as isolated particles The elementary degrees of freedom are not observed free in Nature. the color electric field energy generated by an isolated quark is calculated to be truly infinite, due to the energy it creates in distant fields
Chiral symmetry breaking: The constituent quark masses are different of the current masses (~0 MeV).