Quantum chromodynamics and Bloom-Gilman duality

We study the quantum-chromodynamic explanation of the long-established empirical connection, called the Bloom-Gilman duality, between scaling and resonance regimes of the inelastic structure function νW2(ω'), where ν and ω' are the usual kinematic variables. We show how QCD expectations for the baryon transition form factors lead to the observed constancy with momentum transfer of the resonance/''background'' ratio. We can also understand why the resonance contribution follows with changing Q2 a curve whose shape is the same as the scaling-limit curve. We comment on the longitudinal response function and on possible contrasts in exciting resonances with different isospins. These await experimental scrutiny in newer-generation electron facilities