Composite nucleons in scalar and vector mean fields.

We emphasize that the composite structure of the nucleon may play quite an important role in nuclear physics. It is shown that the momentum-dependent repulsive force of second order in the scalar field, which plays an important role in Dirac phenomenology, can be found in the quark-meson coupling (QMC) model, and that the properties of nuclear matter are well described through the quarkscalar density in a nucleon and a self-consistency condition for the scalar field. The difference between theories of point-like nucleons and composite ones may be seen in the change of the ω-meson mass in nuclear matter if the composite nature of the nucleon suppresses contributions from nucleon-antinucleon pair creation. PACS numbers: 12.39.Ba,21.65.+f,24.85.+p [email protected] [email protected]