Nguyen Tien Zung, Institut de Mathématiques de Toulouse
Torus actions in normalization problems of dynamical systems

All dynamical system, including non-hamiltonian and non-integrable ones, admits a natural intrinsic commutative symmetry group (torus action) which preserves not only the system but also any tensor field which is invariant with respect to the system. I will discuss the role played by these torus actions in the normalization problems, including action-angle variables, Poincare-Birkhoff normalization, and renormalization group method. Joint Strings-Geolis seminar.