Spin force dependence of the parton distributions: the ratio   $F_2^n(x,Q^2)/F_2^p(x,Q^2)$
  Light-front Hamiltonian dynamics is used to relate low-energy constituent quark models to deep inelastic unpolarized structure functions of the nucleon. The approach incorporates the correct Pauli principle prescription consistently and it allows a transparent investigation of the effects due to the spin-dependent SU(6)-breaking terms in the quark model Hamiltonian. Both Goldstone-boson-exchange interaction and hyperfine-potential models are discussed in a unified scheme and a detailed comparison, between the two(apparently) different potential prescriptions, is presented. 
B. Pasquini (1 and 3), M. Traini (2 and 3), and S. Boffi (4 and 5)   ((1) ECT Trento, (2) University of Trento, (3) INFN Tre...