Periodic solutions of elliptic type for strongly nonlinear Hamiltonian systems
Gianfausto Dell’Antonio, Biancamaria D’Onofrio, Ivar Ekeland · Birkhäuser Basel eBooks · 1995
It is shown that, for autonomous Hamiltonian systems, every convex energy level which is symmetric with respect to the origin carries a periodic solution of elliptic type. An extension is given to nonautonomous systems.