Radial excited states of the nucleon in quark models with dynamical   confinement
  The Roper state is described in the framework of the chiral chromodielectric model as a single quark excitation in self-consistent meson potentials. The interplay between quark and meson excitations is discussed and we emphasise the role of non-quark degrees of freedom in the electroproduction of nucleon excitations. 
M. Fiolhais, P. Alberto, B. Golli and S. Sirca