The main learning objective is to provide the fundamentals of elementary theory of dynamical systems, with particular reference to chaos arising from deterministic systems on the one hand, and to ordered dynamics on the other hand.
Expected learning outcomes
Ther students will acquire knowledge and skilsl towards some relevant results of the theory of dynamical systems.
Lesson period: Second semester
(In case of multiple editions, please check the period, as it may vary)
The goal of the second part of the course is to give a Mathematical description of the chaotic behaviour related to the homoclinic intersection. In particular we will prove that a weakly forced pendulum exhibits chaotic orbits.
Stable manifold theorem: existence and regularity of the stable manifold at a hyperbolic equilibrium point; global stable manifold. The problem of global behviour of the stable manifold. Homoclininc intersection. Poincaré's description of chaotic dynamics. Hyperbolic sets and chaotic behviour: Definition and elementary examples (Arnold's cat, Baker's map). Symbolic dynamic, Bernoulli shift. Some examples of equivalence between a dynamical system and coin's toss. Hyperbolicity of the homoclinic intersection set (in the case of transversal intersection). Shadowing Lemma and applications: Statement and proof. Application to the chaotic behaviour in the neighbourhood of a homoclinic intersection point. Melnikov's method for the proof of the existence of transversal homoclinic intersections. Application to the forced pendulum.
Second part: Poincare' theorem of continuation of periodic orbits. Formulation of the problem in terms of Poincare' map. Streightening theorem, Regularity of Poincare' map Linearization of the Poincare' map, Floquet multipliers, Poincare' Theorem. Applications: Lyapunov center theorem, MacKay and Aubry's Theorem on breathers in lattices of coupled oscillators.
Third part: order.
This part is around Siegel linearization theorem.
Classical theory of linearization of a system in the neighbourhood of an equilibrium point. Normal form, formal theory. The problem: does there exist a coordinate transformation conjugating the system to its linear part? Small denominators. Poincare' domains, Siegel domains, Diophantine type theorems. Siegel theorem.
Prerequisites for admission
Existence and uniqueness for differential equations. Implicit function theorem.
V.I. Arnold: Metodi geometrici della teoria delle equazioni differenziali ordinarie. Roma : Editori Riuniti, 1989.
Earl A. Coddington, Norman Levinson: Theory of ordinary differential equations. New York : McGraw-Hill Book Company, 1955.
V.I. Arnold, Andre' Avez:Problemes ergodiques de la mecanique classique. Paris : Gauthier-Villars, 1967.
Anatole Katok, Boris Hasselblatt: Introduction to the modern theory of dynamical systems. Cambridge : Cambridge University Press, 1995.
Assessment methods and Criteria
The final examination consists of an oral exam. The student can choose between two possibilities: 1 a seminar on some topic decided with the professor, 2 answer some questions on the topics presented during the course.