Resumen de Two Action-Angle Surprises on the Sphere

Larry Bates, Richard Cushman

• The linearized Poincaré map of a periodic orbit of a completely integrable Hamiltonian system is examined in the light of the finer description we get by using coordinate changes in the Lagrangian odd symplectic group. In particular, we obtain non-eigenvalue invariants called moduli. These invariants are surprisingly subtle to calculate even in the case of the geodesic flow on a 2-sphere, and reveal dynamic-geometric information that is otherwise symplectically invisible.