Summary Talk on Quark-hadron Duality *

I ascribe the origin of Bloom-Gilman duality in DIS to a separation of scales between the hard subprocess and soft resonance formation. The success of duality indicates that the subprocesses of exclusive form factors are the same as in DIS. The observed dominance of the longitudinal structure function at large x in πN → µ + µ − X can explain why local duality works for DIS with a pion target. The failure of duality in semi-exclusive processes indicates that high momentum transfer t is not sufficient to make the corresponding subprocesses compact. This meeting a demonstrated the exciting progress made in the last few years on duality in Deep Inelastic Scattering (DIS). Building on the work of Bloom and Gilman 1 35 years ago, high precision data principally from Jlab 2,3 and DESY 4 has reopened the field, allowing detailed studies of dual-ity including spin dependence and nuclear effects. In this written summary I focus on just a few aspects of duality that I think give clues to the underlying QCD dynamics. I refer to the presentations given at the workshop for the many important results that I cannot cover here. The comprehensive review 5 by Melnitchouk, Ent and Keppel covers the experimental and theoretical results on duality available before the workshop. 1. Duality and the uncertainty relation The duality between resonances and hard perturbative processes is most easily visualized in e + e − annihilations, where vector mesons average the * Work partially supported by the Academy of Finland through grant 102046.