We study some properties of Lipschitz exact Lagrangian manifolds isotopic to the zero section. We prove that if such a manifold is invariant under an optical Hamiltonian, then it must be a Lipschitz graph. This extends a recent result of Marie-Claude Arnaud. We also obtain a new geometric description of the Mañé-Mather invariant set. —– Résumé. On étudie quelques propriétés des variétés exactes...
