This book is an overview of logarithmic Sobolev inequalities. These inequalities have been the subject of intense activity in recent years, from analysis and geometry in finite and infinite dimensions to probability theory and statistical mechanics. And many developments are still to come. The book is a "pedestrian approach" to logarithmic Sobolev inequalities, accessible to a wide audience. It is divided into several chapters of independent interest. The fundamental example of the Bernoulli and Gaussian distributions is the starting point for logarithmic Sobolev inequalities, as they were defined by Gross in the midseventies. Hypercontractivity and tensorisation form two main aspects of these inequalities, which are actually part of the larger family of classical Sobolev inequalities in functional analysis. A chapter is devoted to the curvaturedimension criterion, which is an efficient tool for establishing functional inequalities. Another chapter describes a characterization of measures which satisfy logarithmic Sobolev or Poincaré inequalities on the real line, using Hardy's inequalities. Interactions with various domains in analysis and probability are developed. A first study deals with the concentration of measure phenomenon, which is useful in statistics as well as geometry. The relationships between logarithmic Sobolev inequalities and the transportation of measures are considered, in particular through their approach to concentration. A control of the speed of convergence to equilibrium of finite state Markov chains is described in terms of the spectral gap and the logarithmic Sobolev constants. The last part is a modern reading of the notion of entropy in information theory and of the several links between information theory and the Euclidean form of the Gaussian logarithmic Sobolev inequality. The genesis of these inequalities can be traced back to the early contributions of Shannon and Stam. This book focuses on the specific methods and the characteristics of particular topics, rather than the most general fields of study. Chapters are mostly selfcontained. The bibliography, without being encyclopedic, tries to give a rather complete state of the art on the topic, including some very recent references. A publication of the Société Mathématique de France, Marseilles (SMF), distributed by the AMS in the U.S., Canada, and Mexico. Orders from other countries should be sent to the SMF. Members of the SMF receive a 30% discount from list. Readership Graduate students and research mathematicians. Table of Contents  Preface
 Avantpropos
 L'exemple des lois de Bernouilli de Gauss
 Sobolev logarithmique et hypercontractivité
 Tensorisation et perturbation
 Familles d'inégalités fonctionnelles
 Le critere de courburedimension
 Inégalités sur la droite réelle
 Concentration de la mesure
 Inégalités de Sobolev logarithmique et de transport
 Sobolev logarithmique et chaines de Markov finies
 Inégalités entropiques en théorie de l'information
 Bibliographie
 Index
