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 quark-scalar 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 $\omega$-meson mass in nuclear matter if the composite nature of the nucleon suppresses contributions from nucleon-antinucleon pair creation.