This volume contains the invited and contributed papers presented at the Fourth International Conference on Perspectives in Hadronic Physics and sent to the Editors within the deadline. The Conference was held at the Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy, from May 12th to 16th, 2003, and was attended by about 100 scientists from 20 countries. The series ofConferences on Perspectives on Hadronic Physics takes place every two years since 1997 and follows the seven Workshops on Perspectives in Nuclear Physics at Intermediate Energies, organized every two years at ICTP since 1983. The aim of these Conferences is to discuss the status-of-the-art concerning the experimental and theoretical investigations of hadronic systems, from nucleons to nuclei and dense nuclear matter, in terms of the relevant underlying degrees of freedom. For such a reason the Fourth Conference has been focused on those experimental and theoretical topics which have been in the last few years the object of intensive investigations, viz. the various approaches employed to describe the structure of hadrons in terms of QCD and QCD inspired models, the recent developments in the treatment of the properties and propagations of hadronic states in the medium, the relevant progress done in the solution of the few- and many- hadron problems, the recent results in the experimental investigation of dense hadronic matter and, last but not least, the physics programs of existing Laboratories and the suggested projects for new Facilities.

This book covers the structure and dynamics of atomic nuclei in terms of nucleons, pions, and quarks, all within a unified treatment of the nuclear response to an electromagnetic probe. The basic formalism is presented to describe the electromagnetic field and its interaction with nuclear matter for both real and virtual photons. Nuclear response is then analyzed in terms of structure functions in the case of inclusive and semi-inclusive inelastic electron scattering. The discussion covers pion production and one- or two-nucleon emission and compares the results with available data. The formalism is also extended to incident polarized electrons, polarized targets and nuclear recoil polarization. It contains a comprehensive description of photonuclear reactions at intermediate energies and a review of experimental data and previous theoretical approaches.