Gauge Invariant States of QCD
  None of the asymptotic states commonly used in perturbative QCD are gauge invariant. A similar statement could be made about QED, but in QED one can construct gauge invariant "dressed" states (with Dirac electrons) that are unitarily equivalent to the states used in perturbation theory. Perturbative expansions of dressed states have been derived for QCD, but Gribov copies obstruct these states from remaining gauge invariant non-perturbatively. Introduced here are new QCD states that are exact solutions to the Dirac condition, so they remain gauge invariant non-perturbatively. The quark content of these states is restricted to be meson-like, baryon-like, or anti-baryon-like locally at each point of space. The states differ from others previously presented due to the use of creation operators defined in coordinate space rather than in momentum space. 
Scott Chapman
nucl-th hep-ph