This book has been prepared to celebrate the 65th birthday of Gabriele Veneziano and his retirement from CERN in September 2007. This reti- ment certainly will not mark the end of his extraordinary scienti?c career (in particular, he will remain on the permanent sta? of the Coll` ege de France in Paris), but we believe that this important step deserves a special celebration, and an appropriate recognition of his monumental contribution to physics. Our initial idea of preparing a volume of Selected papers of Professor Gabriele Veneziano, possibly with some added commentary, was dismissed when we realized that this format of book, very popular in former times, has become redundant today because of the full “digitalization” of all important physical journals, and their availability online in the electronic archives. We have thus preferred an alternative (and unconventional, but probably more e?ective) form of celebrating Gabriele’s birthday: a collection of new papers written by his main collaborators and friends on the various aspects of th- retical physics that have been the object of his research work, during his long and fruitful career.

The Louis de Broglie Foundation (which was created in 1973, for the fiftieth anniversary of the discovery of wave mechanics) and the University of Perugia, have offered an international symposium to Louis de Broglie on his 90th birthday. This publication re presents the Proceedings of this conference which was held in Perugia on April 22-30, 1982. It was an opportunity for the developing of physical conceptions of all origins, which may serve to throw light on the mysterious power of the quantum theory. Quantum Mechanics has reached matu rity in its formalism and although no experiment yet has come to challenge its predictions, one may question the limits of its va lidity. In fact the true meaning of this vision of the microphysi cal world remains the subject of endless debating, at the heart of which lies "the foundational myth" of wave-particle dualism. Albert Einstein and Louis de Broglie are the two discoverers of this fundamental duality, which they always considered as a deep physical reality rather than a phenomenological artifice. During the conference a survey has been given of the essential recent experimental results in corpuscular and quantum optics and the most up-to-date theoretical aspects of the specificity of mi crophysical phenomena : various interpretations of quantum mecha nics, "al ternati ve theories" and hidden parameters theories, pro· babilistic and axiomatic questions and tentative crucial experi ments. The conference took place in the magnificent atmosphere of the villa Colombella lent to us by the Universita per Stranieri di Perugia