Centre de Physique des Houches – serie

Starbursts are regions of unusually rapid star formation, often located in the central parts of galaxies. They differ from more normal regions of star formation in terms of the throughput of mass and the rapidity with which the gas is consumed. In the last twenty years, extensive observational data at most wavelengths have become available on starbursts, but many important issues remain to be addressed, observationally as well as theoretically. How are strong episodes of star formation triggered? What is the quantity of gas converted into stars during bursts? What is the initial mass function of stars in these events? How does the feedback from stars influence the interstellar medium and self-regulate star formation? What is the subsequent chemical and photometric evolution? How do starbursts rule the formation and evolution of galaxies? In recent years, many observational data at different wavelengths (optical, radio, infrared, X-ray) have become available. However, these observations are still fragmentary in the sense that different classes of objects have been observed in different ways, and the coverage is not consistently deep or complete. As a consequence, an overall observational picture of starburst galaxies is missing, and theoretical understanding and modelling have remained highly tentative. The purpose of the school Starbursts: Triggers, Nature, and Evolution was to gather theorists and observers with complementary approaches to the starburst phenomenon, in order to summarize the state-of-the-art of the observations and models, emphasizing the consistency of the various viewpoints.

Branching is probably the most common mode of growth in Nature. From plants to river networks, from lung and kidney to snow-flakes or lightning sparks, branches grow and blossom everywhere, in every realm of Nature. When Galileo Galilei stated that the geometry ofNature was written in terms ofplanes, cones and spheres, he missed one essential pattern of Nature: the tree. However, the tree has been recognized as a "scientific" objet very early, ever since the classical times. Pliny, Strabo or Theophrastus were weIl aware ofthe existence of"dendrites", i. e. , stones in the shape of plants or corals, although the existence of such stones was a puzzle to them. In his book Prodromus Cristallographiae, in which the very word cristallography appears in print for the first time (1711), Mauricius CapeIler, a Swiss naturalist, shows in between facetted crystals, several examples of dendritic crystals. He seemed already to believe in the existence of a general class of branching structures (arbusculatum in modum) in Nature. In the same spirit, his friend Jean-Jacques Scheuchzer had demonstrated experimentally that viscous fingering could generate geological dendrites (1699).At the time of Renaissance, Leornardo da Vinci was quite interested in the resemblance between trees and vessels (1508), and later, Nicola Steno did not hesitate in considering branched deposits of silver found in mines as a close relative of snow.

The discovery of bright visible light emission from porous silicon has opened the door to various nanometer sized silicon structures where the confinement of carriers gives rise to interesting physical properties. While the high efficiency of the light emission in the visible range is the common and the most prominent feature, their structures display similar properties with other highly divided materials (even non semiconductors), and then justify a multidisciplinary approach. This along with potential applications has attracted a large number of researchers followed by students to be trained. Until now international conferences have provided the exchange of information but have remained highly specialised so it was time to give thought to the organisation of topical and advanced lectures where the multidisciplinarity and the didactic approach are paramount. L'ecole des Houches was ideally devoted to that purpose. The meeting : " Luminescence of porous silicon and silicon nanostructures" was the first international school on this topic but some aspects in the organisation and the attendance have given an international workshop flavor to it. The school by itself has trained 82 «students», most of them were students starting their Ph. D thesis. 50% were French citizens and the other represented countries were Germany, England, USA, Czechoslovakia, The Netherlands, Italy, Japan, Poland, Spain, Canada, Brazil, India and Russia.

In the last few years, hopes have emerged that simple concepts could perhaps explain the extremely complicated biomolecular processes which are now known to a greater accuracy. In parallel, powerful methods in physics, especially nonlinearity and co-operative effects, have been developed. They apply especially to biological phenomena and can explain coherent excitations with remarkable properties. This book provides a pedagogical introduction to the theory of nonlinear excitations and solutions in a biological environment, and also to the structure and function of biomolecules as well as energy and charge transport in biophysics.

This book is the collection of most of the written versions of the Courses given at the Winter School "Beyond Quasicrystals" in Les Houches (March 7-18, 1994). The School gathered lecturers and participants from all over the world and was prepared in the spirit of a general effort to promote theoretical and experimental interdisciplinary communication between mathematicians, theoretical and experimental physicists on the topic of the nature of geometric order in solids beyond standard periodicity and quasi periodicity. The overall structure of the book reflects the wish of the editors to pose this fundamental question of geometric order in solids from both the experimental and theoretical point of view. The first part is devoted more specifically to quasicrystals. These materials were the common starting point of most of the audience and present a first concrete example of a non-trivial geometric order. We chose to focus on a few fundamental aspects of quasicrystals related to hidden symmetries in solids which are not easily found in standard textbooks on the topic, not to reach an exhaustive survey which is already available elsewhere.

It is now generally agreed that a deeper understanding of biological processes requires a multi-disciplinary approach employing the tools of biology, chemistry, and physics. Such understanding involves study of biomacromolecules and their functions, which includes how they interact, their reactions, and how information is transmitted between them. This volume is devoted to quantum mechanical simulation techniques, which have developed rapidly in recent years. It covers quantum mechanical calculations of large systems, molecular dynamics combining quantum and classical algorithms, quantum dynamical simulations, and electron and proton transfer processes in proteins and in solutions.

Catalytic reactions on metals are still nowadays involved in more than half of the chemical industrial processes. The winter school held at "I 'Ecole de in March 1996, 13 years after the first one, accounts Physique des Houches" for an evolution of the field in several directions. First, the emulation between theoretical chemistry and solid state physics has emerged on heuristic concepts, leading not only to explanations of the observed phenomena but, for the first time, to predictions of the reactivity of catalytic systems and of the reaction pathways. The second domain which during these years has become of primary importance is the abatement of the pollution. It concerns not only the conversion of polluting effluents but more and more major modifications of the processes to avoid the production of undesired products. Two striking examples are the necessary catalytic conversion of the 100 000 cubic meter of hydrogen that would be produced in a major incident of a nuclear power plant and the replacement of the CFC. The valorization of agricultural supplies can already be considered as one of the major achievement of catalysis. Indeed, the carbon of biosustainable raw materials represents more than 2 orders of magnitude the amount extracted from fossil fuels each year. Moreover, the molecules are already highly functionalised in contrast with hydrocarbons which require costly steps to be converted to the same products. They are now of current use in the elaboration of cosmetics, vitamins, polymers, etc.

This book is an excellent introduction to the concept of scale invariance, which is a growing field of research with wide applications. It describes where and how symmetry under scale transformation (and its various forms of partial breakdown) can be used to analyze solutions of a problem without the need to explicitly solve it. The first part gives descriptions of tools and concepts; the second is devoted to recent attempts to go beyond the invariance or symmetry breaking, to discuss causes and consequences, and to extract useful information about the system. Examples are carefully worked out in fields as diverse as condensed matter physics, population dynamics, earthquake physics, turbulence, cosmology and finance.

Among the several distinct ways of formulating and quantizing a Hamiltonian system, the light cone approach enjoys special status because it has the largest stability group. The aim of this volume is to present recent achievements and open problems in this rather unusual quantization framework to a large audience. The formulation is set up in a comprehensive introduction where the issues are also clearly indicated with specific examples: vacuum structure, signature of non-perturbative effects, chiral symmetry breaking, light cone gauge theories, etc. The following chapters address these topics through a selection of the most relevant contributions presented at Les Houches.This volume should prove valuable to newcomers in the field, and graduates and academics.

Starbursts are regions of unusually rapid star formation often located in the central parts of galaxies. Recent observational and theoretical developments have emphasized their importance to understand the connection between star formation, the interstellar medium, and the secular evolution of galaxies. In this book, leading experts in the field introduce the basic processes involved in the physics of starbursts, the phenomenological concepts which are used to describe and model their triggering and evolution, and their link to galaxy formation and history. A specific effort is made to start with pedagogical presentations and to review the state-of-the art of the observations and models, emphasizing the recent breakthroughs and the major issues to be explored in the future.

The 1997 Les Houches workshop on "Dynamical Network in Physics and Biology" was the third in a series of meetings "At the Frontier between Physics and Biology". Our objective with these workshops is to create a truly interdisciplinary forum for researchers working on outstanding problems in biology, but using different approaches (physical, chemical or biological). Generally speaking, the biologists are trained in the particular and motivated by the specifics, while, in contrast, the physicists deal with generic and "universal" models. All agree about the necessity of developing "robust" models. The specific aim of the workshop was to bridge the gap between physics and biology in the particular field of interconnected dynamical networks. The proper functioning of a living organism of any complexity requires the coordinated activity of a great number of "units". Units, or, in physical terms, degrees of freedom that couple to one another, typically form networks. The physical or biological properties of interconnected networks may drastically differ from those of the individual units: the whole is not simply an assembly of its parts, as can be demonstrated by the following examples. Above a certain (critical) concentration the metallic islands, randomly distributed in an insulating matrix, form an interconnected network. At this point the macroscopic conductivity of the system becomes finite and the amorphous metal is capable of carrying current. The value of the macroscopic conductivity typically is very different from the conductivity of the individual metallic islands.

1 2 V. E. Zakharov and S. Wabnitz 1 L. D. Landau Institute for Theoretical Physics, 2 Kosygin Str. , 117334 Moscow, Russia 2 Laboratoire de Physique, University of Bourgogne, 9 avenue A. Savary, 21078 Dijon, France After about a quarter of a century since the first theoretical predictions of op­ tical solitons, the industrial application of the optical soliton concept is near to reality in the booming field of modern telecommunications, where the de­ mand for high-speed data transmission and routing is of ever-growing. This book contains a set of lectures that were presented at a Les Houches school on optical solitons in September 1998. The school was successful in gathering among the lecturers most of the well-recognized world leaders in the field of optical solitons. A variety of different aspects of research into optical solitons was exposed in the lectures, ranging from the mathematical fundations of integrability theory to the rapidly evolving technological advances of fiber soliton-based telecommu­ nication systems. The overall impression that the participants and the students received from the school is that this field of research is an excellent example of the rapid transfer that occurs nowadays from basic science to the technological implementations of the first principles. The subjects that were covered by the lectures can be broadly grouped into four main categories: optical soliton the­ ory, fiber soliton telecommunications, optical soliton generation methods, and all-optical information processing via spatial solitons.