Nonlinear dynamics is concerned with phenomena evolving in time, which are modelled by differential equations (ordinary, partial, or functional differential equations) and difference equations. The issues studied are: the geometrical description of solutions (individually or as a whole), their asymptotic behavior, families of dynamical systems depending on parameters and their bifurcations, the controllability of systems, the sensitivity to perturbations, optimality conditions.
The main purpose of this program is to develop simultaneously some aspects of mathematical dynamics to favour exchanges among researchers in various branches and to offer students a training as complete as possible. These aspects are:
Various techniques arise in the program. These include topological methods for proving existence of solutions; algebraic-geometric methods (the study of polynomial vector fields is currently very active); variational methods; the techniques of control theory, both theoretical (for example, non-smooth analysis) and numerical; the theory of fractals with applications to rough surfaces, porous surfaces, different types of aggregations, and percolation theory; ergodic theory and methods of Markov chains. There is emphasis on biological models arising in physiology, epidemiology, population dynamics, and genetics.
Students are expected to acquire the fundamentals of analysis, differential equations, and, when required, probability theory. Students are then expected to take a number of more specialized courses offered within the program.
Flots discrets et continus. Équations différentielles non linéaires, techniques classiques d’analyse de dynamique, existence et stabilité de solutions, variétés invariantes, bifurcations, formes normales, systèmes chaotiques. Applications moderne.
Rappels sur les systèmes linéaires. Systèmes non linéaires : linéarisation et méthode de Lyapounov. Solutions périodiques : application de Poincaré, théorème de Poincaré-Bendixon. Variétés répulsives et attractives. Introduction à la stabilité structurelle et théorème de Peixoto. Variétés neutres, formes normales et application à la théorie locale des bifurcations. Exemple de Smale et bifurcation de points homocliniques.