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The 1989 Cargese Summer Institute on Particle Physics was organized by the Universite Pierre et Marie Curie, Paris (M. Levy and J.-L. Basdevant), CERN (M. Jacob), the Universite Catholique de Louvain (D. Speiser and J. Weyers) and the Katholieke Universiteit te Leuven (R. Gastmans), which, since 1975, have joined their efforts and worked in common. It was the twenty-sixth Summer Institute held at Cargese and the tenth organized by the two Institutes of Theoretical Physics at Leuven and Louvain-la-Neuve. The 1989 school centered on the following topics - new experimental results - strings, superstrings and conformal field theory - lattice approximations. Of the many new experimental results, we would like to mention especially those from SLAC presented by Professor G. Feldman. On the other hand, we had the tantalizing knowledge that LEP would begin to operate only right after the end of the school! For this we received ample replacement: Professor J. Steinberger summed up all major CP violation experiments done to date and commented upon them. The reader will find also various other most interesting contributions, for instance on high energy ion beams. Once more theoreticians and experimentalists (this time more than usual) came together to discuss high energy particle physics.

These proceedings are based upon the invited review papers and the research notes presented at the NATO Advanced Research Institute on "Artificial Particle Beams in Space Plasma Studies" held at Geilo, Norway April 21-26, 1981. In the last decade a number of research groups have employed artificial particle beams both from sounding rockets and satellites in order to study various ionospheric and magnetospheric phenomena. However, the artificial particle beams used in this manner have given rise to a number of puzzling effects. Thus, instead of being just a probe for studying the ambient magnetosphere, the artificial particle beams have presented a rich variety of plasma physics problems, in parti~ular various discharge phenomena, which in themselves are worthy of a careful study. The experimental studies in space using artificial particle beams have in turn given rise to both theore­ tical and laboratory studies. In the laboratory experi­ ments special attention has been paid to the problem of creating spacelike conditions in the vacuum chamber. The theoretical. work has addressed the question of beam­ plasma-neutral interaction with emphasis on the wave generation and the modified energy distributions of the charged particles. Numerical simulations have been used extensively. With the advent of the Space Shuttle in which several artificial particle beam experiments are planned for the 1980's, there is a growing interest in such experiments. Furthermore, there is a need for coordinating these studies, both in space and in the laboratory.

Before you lies the proceedings oft he NATO Advanced Study Institute/Newton Institute Workshop ¿Confinement, duality and non perturbative aspects of QCD¿. The school covered the most important techniques to study Quantum Chromodynamics (QCD) andconfinement, fromlattice gauge theory, through Wilson¿s renormalisation group, to electromagnetic duality. The organisingcommittee existed of: Ian Drummond (DAMTP, Cambridge), Mikhail Shifman (Minneapolis), Peter West (King¿s, London), and Pierrevan Baal (Leiden), who acted as director oft he school. This summer school was the concluding activity ofa six month programme on ¿Non perturbative Aspects of Qua ntum Field Theory¿ taking place at the Isaac Newton Institute for Mathematical Sciences in Ca mbridge, UK,whic h started in January 1997, organised by David Olive, Pierre van Baal, and Peter West. A large number ofthe lecturers also participated in the programme and a few programme participants were asked to present a seminar at the school. Not contained in these proceedings are the seminars by Peter Landshoff (DAMTP, Cambridge) on ¿The Pomeron¿ and Ludwig Faddeev (Steklov Math. Inst. , St. Petersburg) on ¿Knot like solitons in 3+1 dimen sional field theory¿. In additiont o the lectures and seminars there were two poster sessions at which participants presented their work. Authors and titles ofthese posters are listed on a separate page. These pro ceedings address the longstanding question of understanding how quarks are confined w ithin subnuclear particles.

Atoms in Intense Laser Fields: Inhibition of Atomic Ionization in Strong Laser Fields; B. Piraux, E. Huens. Optical Analogs of Model Atoms in Fields; P.W. Milonni. Molecules in Intense Laser Fields: Intense Field Dynamics of Diatomic Molecules; L.F. DiMauro, et al. Excitation of Molecular Hydrogen in Intense Laser Fields; H. Helm, et al. High Intensity Molecular Multiphoton Ionization; G.N. Gibson, et al. Atomic Coherences: Coherence in Strong Field Harmonic Generation; A. L'Huillier, et al. Coherent Interactions within the Atomic Continuum; P. Lambropoulos, et al. Molecular Coherences: Femtosecond Pulse Shaping and Excitation of Molecular Coherences; A.M. Weiner, et al. Coherence in the Control of Molecular Processes; P. Brumer, M. Shapiro. Optimal Control of Molecular Motion; H. Rabitz. 25 additional articles. Index.

There is no doubt that we have, during the last decade, moved into a "golden age" of condensed matter science. The sequence of discoveries of novel new states of matter and their rapid assimilation into experimental and theoretical research, as well as devices, has been remarkable. To name but a few: spin glasses; incommensurate, fractal, quasicrystal structures; synthetic metals; quantum well fabrication; fractional quantum Hall effect: solid state chaos; heavy fermions; and most spectacularly high-temperature superconductivity. This rapid evolution has been marked by the need to address the reality of materials in "extreme" conditions - - disordered, nonlinear systems in reduced dimensions, restricted geometries and at mesoscopic scales, often with striking competitions between several length and frequency scales, and between strong electron-phonon and electron-electron interactions. In such new territory it is not surprising that very interdisciplinary approaches are being explored and traditional boundaries between subjects and disciplines re-defined. In theory, this is evident, for instance, in attempts: (1) to advance the state of the art for elec­ tronic structure calculations so as to handle strongly interacting many-body systems and delicate competitions for collective ground states (spin models or many-electron Hamiltoni­ ans, field theory, band structure, quantum chemistry and numerical approaches); or (2) to understand pattern formation and complex (including chaotic) dynamics in extended sys­ tems. This demands close involvement with applied mathematics, numerical simulations and statistical mechanics techniques.

The rediscovery of fast ion conduction in solids in the 1960's stimulated interest both in the scientific community in which the fundamentals of diffusion, order-disorder phenomena and crystal structure evaluation required re-examination, and in the technical community in which novel approaches to energy conversion and chemical sensing became possible with the introduction of the new field of "Solid State Ionics. " Because of both the novelty and the vitality of this field, it has grown rapidly in many directions. This growth has included the discovery of many new crystalline fast ion conductors, and the extension to the fields of organic and amorphous compounds. The growth has involved the extension of classical diffusion theory in an attempt to account for carrier interactions and the development of sophisticated computer models. Diffraction techniques have been refined to detect carrier distributions and anharmonic vibrations. Similar advances in the application of other techniques such as NMR, Raman, IR, and Impedance Spectroscopies to this field have also occurred. The applications of fast ion conducting solid electrolytes have also developed in many directions. High energy density Na/S batteries are now reaching the last stages of development, Li batteries are being implanted in humans for heart pacemakers, and solid state fuel cells are again being considered for future power plants. The proliferation of inexpensive microcomputers has stimulated the need for improved chemical sensors--a major application now being the zirconia auto exhaust sensor being sold by the millions each year.

This book contains all the papers presented at the NATO workshop on "Optical Switching in Low Dimensional Systems" held in Marbella, Spain from October 6th to 8th, 1988. Optical switching is a basic function for optical data processing, which is of technological interest because of its potential parallelism and its potential speed. Semiconductors which exhibit resonance enhanced optical nonlinearities in the frequency range close to the band edge are the most intensively studied materials for optical bistability and fast gate operation. Modern crystal growth techniques, particularly molecular beam epitaxy, allow the manufacture of semiconductor microstructures such as quantum wells, quantum wires and quantum dots in which the electrons are only free to move in two, one or zero dimensions, of the optically excited electron-hole pairs in these low respectively. The spatial confinement dimensional structures gives rise to an enhancement of the excitonic nonlinearities. Furthermore, the variations of the microstruture extensions, of the compositions, and of the doping offer great new flexibility in engineering the desired optical properties. Recently, organic chain molecules (such as polydiacetilene) which are different realizations of one dimensional electronic systems, have been shown also to have interesting optical nonlinearities. Both the development and study of optical and electro-optical devices, as well as experimental and theoretical investigations of the underlying optical nonlinearities, are contained in this book.

A NATO workshop on "The Properties of Impurity States in Semiconductor Superlattices" was held at the University of Essex, Colchester, United Kingdom, from September 7 to 11, 1987. Doped semiconductor superlattices not only provide a unique opportunity for studying low dimensional electronic behavior, they can also be custom-designed to exhibit many other fascinating el~ctronic properties. The possibility of using these materials for new and novel devices has further induced many astonishing advances, especially in recent years. The purpose of this workshop was to review both advances in the state of the art and recent results in various areas of semiconductor superlattice research, including: (i) growth and characterization techniques, (ii) deep and shallow im­ purity states, (iii) quantum well states, and (iv) two-dimensional conduction and other novel electronic properties. This volume consists of all the papers presented at the workshop. Chapters 1-6 are concerned with growth and characterization techniques for superlattice semiconductors. The question of a-layer is also discussed in this section. Chapters 7-15 contain a discussion of various aspects of the impurity states. Chapters 16- 22 are devoted to quantum well states. Finally, two-dimensional conduction and other electronic properties are described in chapters 23-26.

A NATO Advanced Study Institute (ASI) on High-Brightness Accelerators was held at the Atholl Palace Hotel, Pitlochry, Perthshire, Scotland, from July 13 through July 25, 1986. This publication is the Proceedings of the Institute. This ASI emphasized the basic physics and engineering of the rela­ tively new and fast-emerging field of high-brightness particle accelera­ tors. These machines are high- to very-high-current (amperes to hundreds of kiloamperes), modest-voltage (megavolt to tens of megavolts) devices, and as such are opposed to those historically used for high-energy physics studies (i.e., gigavolt and higher energies and rather low currents). The primary focus of the Institute was on the physics of the accelerator and the beam, including the dynamics, equilibria, and insta­ bilities of high-current beams near the space-charge limit; accelerator engineering techniques; and the applications of high-brightness beams in areas such as free-electron lasers, synchrotron-radiation sources, food processing, and heavy- and light-ion fusion. The Institute concentrated on bringing together several diverse but related communities which, we hope, benefited from this opportunity to interact: the North American activity in machine technology, engineer­ ing, and diagnostics with the strong European theoretical community; the basic beam physicists with the engineering technologists.

The Advancea Kesearch Workshop on Superstrings was held on the campus of the University of Colorado at Boulder from July 27th through August 1, 1987. Since the work of Green and Schwartz in the summer of 1984, string theories have elicited tremendous amount of interest from both theoretical physicists and mathematicians. The objective of the Workshop was to bring together practitioners in the field to discuss the progress and problems, and possible directions of future research. There were ten talks of one hour each and twenty three talks of one-half hour each. The talks covered new formulations and technical developments. There were intense discussions both during and at the end of the lectures; 'further discussions continued during lunch and dinner. These proceedings contain all talks given at the Workshop except those by Victor Kac, Darwin Chang and Doron Gepner. The Workshop was sponsored by the North Atlantic Treaty Organization, which provided generous financial support enabling many young physicists from the U.S. and abroad to participate in the Workshop. Additional co-sponsors were the U.S. Department of Energy and the University of Colorado. The former offered further financial assistance and the latter furnished clerical and technical services and its campus facilities for the purpose of the organization and running of the Workshop. The International Organizing Committee consisted of John Ellis, Francois Englert, Peter G.O. Freund (co-director), K. T. Mahanthappa (co-director) and Abdus Salam.

This volume represents the proceedings of a NATO Advanced Study Institute held at Noto, Sicily June 8-19, 1987. The director was Giovanni Gallavotti, Roma, with co-directors Marcello Anile, Catania and P. F. Zweifel, Virginia Tech. Other members of the scientific organizing committee included Mitchell Feigenbaum, Rockefeller University and David Ruelle, IHES. The attendance at the school consisted of 23 invited speakers and approximately 80 "students", the term student being in quotation marks because many of them were of post-doctoral or even professorial status, although there were also a goodly number of actual graduate students in attendance also. Because of the disparate background of these "students", it was felt advisable to include at the conference special tutorials each afternoon, in which the contents of the morning's lectures were reviewed and clarified as necessary. These tutorials, organized by Gallavotti, involved various of the speakers, organizers, and other senior members of the school, and contributed in no little way to the overall success of the school. The organizers of the school would like to take this opportunity to thank all of those who assisted in these sessions, and to assure them that the results were definitely worth the effort. Also contributing to the success of the school were a number of contributed papers, presented during the course of the afternoon tutorials. Three of those papers are included in these proceedings; they are the papers of DiFrancesco; Gallimbeni, Miari and Sertorio (presented by Sertorio); and Vittot.

Acquired immune deficiency syndrome (AIDS) poses a health threat unparalleled in modem times. Identified just a few years ago, AIDS and the human inunlmodeficiency virus (IDV) responsible for it affect millions of persons worldwide. AIDS has already become the leading cause of death among persons under 40 in some large American cities. From the beginning. it has been evident that AIDS carries unique psychological and social ramifications. In spite of its lethality, new cases of HIV infection are preventable if individuals can be assisted to make behavior changes to lessen or eliminate viral transmission. To the extent that we can develop effective primary prevention interventions, it will be possible to keep larger numbers of people from becoming infected with the mv virus. Psychological and social risk­ behavior change interventions, whether at the level of individual clients, groups, or entire communities, can playa key role-in fact, the only available role-in disease prevention. Patients with any life-threatening illness have psychological, social, and support needs. However, these needs are more pronounced and, often, less easily addressed for persons affected by AIDS. People in good clinical health but with HIV infection face years of worry concerning whether they will develop AIDS. Nearly 2 million Americans are currently in this precarious position; by 1991, 50 to 100 million persons worldwide are expected to share the same uncertainty.

This book contains the lectures delivered at the NATO Advanced Study Institute on "Physics and Applications of Quantum Wells and Superlattices", held in Erice, Italy, on April 21-May 1, 1987. This course was the fourth one of the International School of Solid-State Device Research, which is under the auspices of the Ettore Majorana Center for Scientific Culture. In the last ten years, we have seen an enormous increase in re­ search in the field of Semiconductor Heterostructures, as evidenced by the large percentage of papers presented in recent international conferences on semiconductor physics. Undoubtfully, this expansion has been made possible by dramatic advances in materials preparation, mostly by molecular beam epitaxy and organometallic chemical vapor deposition. The emphasis on epitaxial growth that was prevalent at the beginning of the decade (thus, the second course of the School, held in 1983, was devoted to Molecular Beam Epitaxy and Heterostructures) has given way to a strong interest in new physical phenomena and new material structures, and to practical applications that are already emerging from them.

With the discovery of pulsars, quasars, and galactic X-ray sources in the late 60's and early 70's, and the coincident expansion in the search for gravitational waves, rela­ tivistic gravity assumed an important place in the astrophysics of localized objects. Only by pushing Einstein's solar-system-tested general theory of relativity to the study of the extremes of gravitational collapse and its outcomes did it seem that one could explain these frontier astronomical phenomena. This conclusion continues to be true today. Relativistic gravity had always played the central role in cosmology. The discov­ ery of the cosmic background radiation in 1965, the increasing understanding of matter physics at high energies in the decades following, and the growing wealth of observations on the large scale structure meant that it was possible to make increasingly detailed mod­ els of the universe, both today and far in the past. This development, not accidentally, was contemporary to that for localized objects described above.

Research activities in low dimensional conductors have shown a rapid growth since 1972 and have led to the discovery of new and remarkable phy­ sical properties unique to both molecular and inorganic conductors exhibi­ ting one-dimensional transport behaviour. This NATO Institute was a conti­ nuation of aseries of NATO Advanced Study Institutes of Worshops which took place at regular intervals till 1979. This is the first time, however, that charge density wave transport and electronic properties of low dimen­ sional organic conductors are treated on an equal footing. The program of the Institute was framed by tutorial lectures in the theories and experiments of low dimensional conductors. The bulk of the course covered two series of low-dimensional mate­ rials with their respective properties. 1) The I-D inorganic conductors exhibiting the phenomena of sliding charge density waves, narrow band noise, memory effects, etc ... 2) Low-dimensional crystallized organic conductors giving rise to various possibilities of ground states, spin-Peierls, spin density wave, Peierls, superconductivity and magnetic-field induced spin density wave, etc ... Since it has been established from the beginning that this Institute was to be devoted essentially to the Physics of Low Dimensional Conductors, only one main course summarized the progress in chemistry and material preparation.

This volume contains the Proceedings of the NATO Advanced Research Workshop on "Optical Properties of Narrow-Gap Low-Dimensional Structures", held from July 29th to August 1st, 1986, in St. Andrews, Scotland, under the auspices of the NATO International Scientific Exchange Program. The workshop was not limited to optical properties of narrow-gap semiconductor structures (Part III). Sessions on, for example, the growth methods and characterization of III-V, II-VI, and IV-VI materials, discussed in Part II, were an integral part of the workshop. Considering the small masses of the carriers in narrow-gap low­ dimensional structures (LOS), in Part I the enhanced band mixing and magnetic field effects are explored in the context of the envelope function approximation. Optical nonlinearities and energy relaxation phenomena applied to the well-known systems of HgCdTe and GaAs/GaAIAs, respectively, are reviewed with comments on their extension to narrow­ gap LOS. The relevance of optical observations in quantum transport studies is illustrated in Part IV. A review of devices based on epitaxial narrow-gap materials defines a frame of reference for future ones based on two-dimensional narrow-gap semiconductors; in addition, an analysis of the physics of quantum well lasers provides a guide to relevant parameters for narrow-gap laser devices for the infrared (Part V). The roles and potentials of special techniques are explored in Part VI, with emphasis on hydrostatic pressure techniques, since this has a pronounced effect in small-mass, narrow-gap, non-parabolic structures.

The four-week period fran May 20 to June 16, 1984 was an intensive period of advanced study on the foundations and frontiers of nonequili­ brium statistical physics (NSP). During the first two weeks of this period, an advanced-study course on the "Foundations of NSP" was con­ ducted in Albuquerque under the sponsorship of the University of New Mexico Center for High-Technology Materials. This was followed by a two-week NATO Advanced Study Insti tute on the "Frontiers of NSP" in Santa Fe under the same directorship. Many Students attended both meetings. This book comprises proceedings based on those lectures and covering a broad spectrum of topics in NSP ranging fran basic problems in quantum measurement theory to analogies between lasers and Darwinian evolution. The various types of quantum distribution functions and their uses are treated by several authors. other tools of NSP, such as Langevin equations, Fokker-Planck equations, and master equations, are developed and applied to areas such as laser physics, plasma physics, Brownian motion, and hydrodynamic instabilities. The properties and experimental detection of squeezed states and antibunching are described, as well as experimental tests of the violation of Bell's inequality. Information theory, mean-field theory, reservoir theory, entropy maximization, and even a novel nonlinear generalization of quantum mechanics are used to discuss nonequilibrium phenanena and the approach toward thermodynamic equilibrium.

The Proceedings of the Advanced study Institute on Fundamental Processes in Atomic Collision Physics (Santa Flavia, Italy, September 10-21, 1984) are dedicated to the memory of Sir Harrie r-1assey, whose scientific achievements and life are reviewed herein by Sir David Bates. At the first School on the above topic (Maratea, September 1983, Volume 103 in this series), Harrie Massey presented the introductory lectures, summarized the entire lecture program, and presented an outlook on future developments in atomic collision physics. In an after-dinner speech, Massey recalled personal reminiscences and historical events with regard to atomic collision physics, to which he had contributed by initiating pioneering work and by stimulating and surveying this branch of physics over a period of almost six decades. Participants in the Maratea School will always remember Harrie Massey as a charming and wonderful person who was most pleased to discuss with everyone--students, postdoctorals, and senior scientists--any topic in atomic collision physics. Harrie Massey was a member of the Scientific Advisory Committee of the 1984 Santa Flavia School. Before his death he expressed his interest in attending this second School devoted to the presentation of recent developments and highlights in atomic collision physics. It is the desire of all authors to honor Harrie Massey with their contributions in these Proceedings.

Prior to the 9th International Conference on Reactivity Solids in Krakow, Poland a group of about 25 international scientists held a special conference entitled "Transport in Nonstoichiometric Compounds" in late Aug. 1980 in Mogilany, Poland (near Krakow). This conference was well received in view of the interaction between the participants, as well as the resulting publication of the proceedings (Elsevier Scientific Publishing Company, 1982, edited by J. Nowotny). At this first conference the participants decided that it would be desirable to organize similar conferences at about two year intervals. Thus, a second meeting was held in late June, early July at Alenya, Pyrenees Orientales, France. This conference had a larger number of participants, about 50, but still managed to promote excellent interaction between all the participants. These proceedings, with editors G. Petot-Ervas, Hj. Matzke and C. Monty, have also been published by Elsevier as a special edition of the journal, Solid State lonics, Vol. 12 (1984). In view of the success of the initial two conferences, a third meeting was organized and held at The Pennsylvania State University, University Park, PA., 16802, U.S.A. from 11 June 84 to 15 June 84. The proceedings of this conference are presented in the following text.

The 1983 Cargese Summer Institute on Particles and Fields was organized by the Universite Pierre et Marie Curie, Paris (M. LEVY and J.-L. BASDEVANT), C.E.R.N. (M. JACOB), the Universite Catholique de Louvain (D. SPEISER and J. WEYERS), and the Katholieke Universiteit Leuven (R. GASTMANS). After 1975, 1977, 1979, and 1981, it was the fifth time they joined their efforts for organizing this Summer Insti­ tute. This school was characterized by simultaneous progress in the theory of elementary particles and by impressive experimental advances. On the theoretical front, one witnessed the new developments in lattice gauge theories, which explore the world of strongly interacting par­ ticles in a non-perturbative way, and progress in a better understan­ ding of the unity of all interactions based on supersymmetry. The experimentalists were ~roud to announce the discovery of the interme­ diate vector bosons; W- and ZO, at C.E.R.N., while physicists working with e+e- colliding beams continued to probe more deeply the validity of the theoretical models of strong, weak and electromagnetic inter­ actions. We owe many thanks to all those who have made this Summer Insti­ tute possible! Thanks are due to the Scientific Committee of NATO and its Presi­ dent for a generous grant and especially to the head of the Advanced Study Institute Program and his collaborators for their constant help and encouragement. We also thank the National Science Foundation (USA) for their financial assistance.

The problem of moment formation in metallic systems lies at the interface of localized and itinerant magnetism. The phenomena observed correspond to destruction rather than to formation of spin-correlations. They give rise to the progression from local­ ized ground states through Kondo and mixed-valence behaviour to itinerant magnetic or non-magnetic systems. Somewhere in the pro­ gression superconductivity can occur in the presence of f-moments. To bring together the disparate ideas and methods, previously the subject of intense debate only at a number of topical confer­ ences, a two-week Advanced Study Institute was held August 21 - September 02, 1983, at Lester B. Pearson College of the Pacific, Vancouver Island. In the stimulating environment provided by the pines and fiord at the site of this remote United World College on the Canadian West Coast, scientists and students from around the globe gathered to hear lectures by experts. The Study Institute involved seventy-six people and followed in the tradition . of pre­ vious "Banff" summer schools organized by the Canadian Association of Physicists. It was made possible by grants from the North Atlantic Treaty Organization, the Natural Sciences & Engineering Research Council of Canada and Atomic Energy of Canada. The grants permitted many young scientists from Nato and non-Nato countries to learn the fundamentals as well as the latest results in the field.

This book presents an account of the NATO Advanced Study Institute on "Energy Transfer Processes in Condensed Matter", held in Erice, Italy, from June 16 to June 30, 1983. This meeting was organized by the International School of Atomic and Molecular Spectroscopy of the "Ettore Majorana" Centre for Scientific Culture. The objective of the Institute was to present a comprehensive treatment of the basic mechanisms by which electronic excitation energy, initially localized in a particular constituent or region of a condensed material, transfers itself to the other parts of the system. Energy transfer processes are important to such varied .fields as spectroscopy, lasers, phosphor technology, artificial solar energy conversion, and photobiology. This meeting was the first encounter of this sort entirely dedicated to this important topic. A total of 65 participants came from 47 laboratories and 16 nations (Belgium, Czechoslovakia, F.R. of Germany, France, Greece, India, Ireland, Israel, Italy, The Netherlands, Poland, Portugal, Switzerland, Turkey, United Kingdom, and the United States of A America). The secretaries of the course were: Ms. Aliki Karipidou for the scientific aspects and Mr. Massimo Minella for the admini­ strative aspects of the meeting.