Two-quark correlations inside baryons play an important role in our understanding of hadronic structures. The Diquarks II workshop was the second on this subject and the proceedings present the most recent contributions and ideas of many experts on the concept of diquarks, their properties and their many applications.

The confinement mechanism of the quarks in QCD is one of the most challenging and open problems in physics. Confinement is a nonperturbative phenomenon, and a definite way to handle it has not yet been found in field theory. There are lattice calculations that can produce the low-lying states of the spectrum and 'measure' many important physical quantities, but nevertheless the development of analytical techniques is of extreme importance for understanding the physics involved in confinement. In this respect it is important to test the results obtained directly from the theory (Bethe-Salpeter kernel, effective Hamiltonians, quark potential, etc.) on the spectrum, form factors and decays of bound states of quarks and gluons, and to relate them to the results of lattice theory.In this book, the question of the confinement mechanism is addressed; explanations in terms of monopoles, instantons and dyons are reviewed and the connection with duality is discussed.

This book is devoted to the investigation of the strongly interacting hadrons ? to a quark model operating with effective color particles, constituent quarks, massive effective gluons and diquarks. The study of strong interactions based on effective constituent particles requires a solid ground of experimental data, which we now have at our disposal with the serious progress made in the investigation of hadrons, especially meson states.The present understanding of QCD applied to strong interactions can be distorted by prejudices. Therefore, the way followed by the quark model is to rely on the experiment and to restore the effective Hamiltonian on the basis of QCD on the one hand, and, on the other, of the spectral integral method.Baryon-baryon and antibaryon-baryon interactions are studied with the purpose of unambiguous applications of the written formulae to the interpretation of experimental data ? to the observation of new meson and baryon resonances. The technique used is the spin-orbital momentum expansion of the amplitude. This method is our basic approach to the proper treatment of experimental data. The photon-induced reactions are also considered and the problem of form factors is discussed.

Although perturbative QCD has progressed much in the last few years, the notion of diquarks is still useful and vital and many short cuts induced by diquarks can still be very efficient for simulating nonperturbative effects in the intermediate energy region (from a few GeV to some 10-20 GeV), where a whole new generation of machines is being planned and will, hopefully, become operative in the near future.

This volume presents a selection of current developments in quantum chromodynamics, with some emphasis on the borderline between the perturbative and the nonperturbative regime. The topics include: effective QCD, sum rules, vacuum structure, confinement, bound states, quark masses, lattice QCD, deconfinement, deep inelastic scattering and structure functions, strong coupling constant, radiative corrections.

The 9th International Symposium on High Energy Spin Physics, held in Bonn, 6-15 September 1990, attracted 280 participants from 16 countries. This meet ing covered not only fundamental experimental and theoretical spin phenomena but also technological developments in polarized beams and targets. For the first time intermediate energy spin physics with electron machines was discussed extensively. Highlights included the work on polarized high energy electron beams at LEP and TRISTAN and the failure of the standard model in connection with spin phenomena, in particular the growth of the spin asymmetry in violent proton-proton scattering. Also the presentation of different models in con nection with the still-unsolved 'proton spin crisis' and the proposals for four different experiments to determine the spin structure functions caused lively and sometimes controversial discussions. The Organizing Committee would like to thank all speakers for their excel lent talks, the conveners for the organization of the parallel sessions, and the International Advisory Committee for their advice. Four workshops preceded the symposium. 160 participants, among them many young physicists, discussed mainly technological spin problems. These papers are published in separate proceedings. We gratefully acknowledge the enthusiastic help of the members of our institute in preparing and running the conference and the workshops, especially Mrs. D. FaSbender, Mrs. E. Wendorf, Mrs. J. Wetzel, and Dr. U.Idschok.

This invaluable book is an extensive set of lecture notes on various aspects of non-perturbative quantum chromodynamics — the fundamental theory of strong interaction on which nuclear and hadronic physics is based.The original edition of the book, written in the mid-1980's, had more of a review style. In the second edition the outline remains the same, but the text has been completely rewritten, and extended. Apart from the new developments over the years, this edition has benefited from several graduate courses which the author has taught at Stony Brook during the last decade. The text is now complemented by exercises and has a total of about 1000 references to major works, arranged by subject.Three major issues — the structure of the QCD vacuum, the structure of hadrons, and the physics of hot/dense matter — are addressed as physics problems. Therefore, when discussing any specific subject, the book attempts to incorporate (1) all the solid theoretical results, (2) experimental information, and (3) results of numerical (lattice) simulations, which are playing an increasing role in quantum field theory in general, and the development of QCD in particular.The QCD Vacuum, Hadrons and Superdense Matter takes the reader from the first encounter with the subject to the front line of research, as quickly as possible.