N ov 1 99 5 RPA Description of the Electric Polarizability of the Nucleon

Excited states of the nucleon are described as RPA configurations on a mean–field ground state taken from the MIT bag model. A residual interaction of a structure as in the Nambu–Jona–Lasinio model is used. The particle-hole states are coupled to good total angular momentum and isospin. Valence excitations of particle-hole type and quark–antiquark (qq) states from the Dirac–sea are included. The dependence of the baryon spectrum and multipole response functions on the coupling constant G is studied. At critical values of G the 3q– ground state becomes degenerate with strongly collective qq modes.