  Based on a recent manifestly covariant time-ordered approach to the
relativistic many-body problem, the quark propagator is defined by a nonlinear
Dyson--Schwinger-type integral equation, with a one-gluon loop. The resulting
energy-dependent quark mass is such that the propagator is singularity-free for
real energies, thus ensuring confinement. The self-energy integral converges
without regularization, due to the chiral limit of the quark mass itself.
Moreover, the integral determines the low-energy limit of the quark-gluon
coupling constant, for which a value of $g^2/4\pi =4.712$ is found.

Nuclear Theory