ABSTRACT
The conjecture turns out to be true in models where one confines these small-mass current quarks within an appropriate potential or a bag of appropriate shape and size. These potential and bag models are widely discussed. In the MIT bag model this confinement is ensured by introducing a bag pressure from outside. However this is performed in an ad-hoc manner. The MIT bag model is constructed to model Quantum Chromodynamics (QCD). The local gauge invariance would demand that one includes gluons in the formalism. One may include gluons, but to avoid double-counting these should be treated only in the lowest order of the perturbation theory.
