Quark effects in nuclear physics

Certain quark effects associated with valence quarks, sea quarks and valence antiquarks are discussed, using the M.I.T. bag model and potential models of quark dynamics. The contributions of valence quarks to many-nucleon forces turn out to be model-dependent, and not well understood. They contain large configuration-mixing effects which appear to arise from certain space-color-spin correlations. These correlations could sometimes cause an abnormal quark matter to collapse. The masses of multiquark states are also sensitive to the confinement mechanism. Sea-quark effects from qantiq fluctuations are shown to be important in nucleon properties. They also give rise to meson-nucleon coupling constants. Valence antiquark effects are discussed in the context of q2antiq2 mesonic spectra. (author)