This volume presents the proceedings of the Workshop on Momentum Distributions held on October 24 to 26, 1988 at Argonne National Laboratory. This workshop was motivated by the enormous progress within the past few years in both experimental and theoretical studies of momentum distributions, by the growing recognition of the importance of momentum distributions to the characterization of quantum many-body systems, and especially by the realization that momentum distribution studies have much in common across the entire range of modern physics. Accordingly, the workshop was unique in that it brought together researchers in nuclear physics, electronic systems, quantum fluids and solids, and particle physics to address the common elements of momentum distribution studies. The topics dis cussed in the workshop spanned more than ten orders of magnitude range in charac teristic energy scales. The workshop included an extraordinary variety of interactions from Coulombic to hard core repulsive, from non-relativistic to extreme relativistic.

This book focuses on the latest theoretical and experimental results and future perspectives regarding electromagnetic and hadronic physics at intermediate energies. Nucleon form factors and spin structure functions, deep-inelastic scattering, excited baryons and mesons, and correlations in nuclei are discussed. Many new results and the scientific programmes of the different laboratories in Europe and North America are also presented. A special section is devoted to relativistic approaches to hadrons and nuclei at intermediate energies.

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.