Are the Dirac particles of the Standard Model dynamically confined states in a higher dimensional flat space?

Some time ago Rubakov and Shaposhnikov suggested that elementary particles might be excitations trapped on a soliton in a flat higher dimensional space. They gave, as an example, phi^4 theory in five dimensions with a bosonic excitation on a domain wall phi cl in the fifth dimension. They also trapped a chiral Dirac particle on the domain wall with the interaction Lagrangian (g psi phi psi). The field equation for the Dirac field was -i zigma 4 mo =o gamma^mo 6mo psi-g phi psi=0. We show that a Dirac equation in eight flat dimensions with -g psi replaced by a harmonicoscillator "potential" in the four higher dimensions (plus a large constant M0) generates bound states in approximate SU (4) x SU (2) représentations. These représentations have corresponding "orbital" times "spin" quantum numbers and bear some resemblance to the quarks and leptons of the Standard Model. Soliton theory suggests that the harmonic-oscillator potential should rise only a finite amount. This will then limit the number of generations in a natural way. It will also mean that particles with sufficient energy might escape the well altogether and propagate freely in the higher dimensions. It may be worthwhile to search for a soliton (instanton?) that can confine Dirac particles in the manner of the harmonic-oscillator potential.