Theory of baryon resonances at large N-c
At large number of colors, N-c quarks in baryons are in a mean field of definite space and flavor symmetry. We write down the general Lorentz and flavor structure of the mean field, and derive the Dirac equation for quarks in that field. The resulting baryon resonances exhibit a hierarchy of scales: the crude mass is O(N-c), the intrinsic quark excitations are O(1), and each intrinsic quark state