Comment on ''Valence QCD: Connecting QCD to the quark model''

The author criticize certain conclusions about the physics of hadrons drawn from a ''valence QCD'' approximation to QCD. Lattice QCD is not just useful as a technique for calculating strong interaction observables like the proton mass: it can also be used to help understand QCD. This is the goal of the work described in reference 1. Its authors present a field theory which they call valence QCD (vQCD) which they hope can be identified with the valence quark model. The key feature built into vQCD is a form of suppression of Z-graphs, i.e., of quarks propagating backward in time. The authors make sound arguments for the importance of trying to capture the essence of the quark model in a field-theoretic framework, and present some interesting results (both theoretical and numerical) on vQCD. This comment is not directed at the goals of vQCD but rather at certain conclusions about the physics of hadrons which the authors have drawn from their work which the author considers unjustified. Foremost among these is the claim highlighted in their abstract that baryon hyperfine interactions are ''largely attributed to the Goldstone boson exchanges between the quarks'' and not to standard one-gluon-exchange (OGE) forces