Symmetry breaking and quark-hadron duality in structure functions

We identify conditions under which a summation over nucleon resonances can yield, via quark-hadron duality, parton model results for electromagnetic and neutrino structure functions at large x. While a summation over the lowest even and odd parity multiplets is sufficient to achieve duality in the symmetric quark model, a suppression of transitions to specific final states is required for more realistic cases incorporating SU(6) breaking. We outline several scenarios consistent with duality, discuss their implications for the high Q^2 behavior of transition form factors, and illustrate how they can expose the patterns in the flavor-spin dependence of inter-quark forces.