In recent years, the classical theory of stochastic integration and stochastic differential equations has been extended to a non-commutative set-up to develop models for quantum noises. The author, a specialist of classical stochastic calculus and martingale theory, tries to provide an introduction to this rapidly expanding field in a way which should be accessible to probabilists familiar with the Ito integral. It can also, on the other hand, provide a means of access to the methods of stochastic calculus for physicists familiar with Fock space analysis. For this second edition, the author has added about 30 pages of new material, mostly on quantum stochastic integrals.

This volume represents a part of the main result obtained by a group of French probabilists, together with the contributions of a number of colleagues, mainly from the USA and Japan. All the papers present new results obtained during the academic year 1991-1992. The main themes of the papers are: quantum probability (P.A. Meyer and S. Attal), stochastic calculus (M. Nagasawa, J.B. Walsh, F. Knight, to name a few authors), fine properties of Brownian motion (Bertoin, Burdzy, Mountford), stochastic differential geometry (Arnaudon, Elworthy), quasi-sure analysis (Lescot, Song, Hirsch). Taken all together, the papers contained in this volume reflect the main directions of the most up-to-date research in probability theory. FROM THE CONTENTS: J.P. Ansal, C. Stricker: Unicite et existence de la loi minimale.- K. Kawazu, H. Tanaka: On the maximum of a diffusion process in a drifted Brownian environment.- P.A. Meyer: Representation de martingales d'operateurs, d'apres Parthasarathy-Sinha.- K. Burdzy: Excursion laws and exceptional points on Brownian paths.- X. Fernique: Convergence en loi de variables aleatoires et de fonctions aleatoires, proprietes de compacite des lois, II.- M. Nagasawa: Principle ofsuperposition and interference of diffusion processes.- F. Knight: Some remarks on mutual windings.- S. Song: Inegalites relatives aux processus d'Ornstein-Ulhenbeck a n-parametres et capacite gaussienne c (n,2).- S. Attal, P.A. Meyer: Interpretation probabiliste et extension des integrales stochastiques non commutatives.- J. Azema, Th. Jeulin, F. Knight, M. Yor: Le theoreme d'arret en une fin d'ensemble previsible.

All the papers contained in the volume are original, fully refereed researchpapers. They represent a fairly broad spectrum of the research activity in probability theory, which was done internationally in 1990-1991, with particular emphasis on Markov processes and stochastic calculus. The latter subject keeps growing, and some important new developments, included in the volume, concern anticipative stochastic integrals, and new applications of the enlargements of filtrations to the study of zeros of martingales. FROM THE CONTENTS: R. Bass, D. Khoshnevisan: Stochastic calculus and the continuity of local times of Levy processes.- M.T. Barlow, P. Imkeller: On some sample path properties of Skorokhod integral processes.- T.S. Mountford: A critical function for the planar Brownian convex hull.- L. Dubins, M. Smorodinsky: The modified, discrete Levy transformation is Bernoulli.- M. Baxter: Markov processes on the boundary of the binary tree.- R. Abraham: Unarbre aleatoire infini associe a l'excursion brownienne.- S.E. Kuznetsov: On the existence of a dual semigroup.

The different papers contained in this volume are all research papers. The main directions of research which are being developed are: quantum probability, semimartingales and stochastic calculus.

Besides a number of papers on classical areas of research in probability such as martingale theory, Malliavin calculus and 2-parameter processes, this new volume of the S minaire de Probabilit?'s develops the following themes: - chaos representation for some new kinds of martingales, - quantum probability, - branching aspects on Brownian excursions, - Brownian motion on a set of rays.