Existence of noncontractible periodic orbits of Hamiltonian system   separating two Lagrangian tori on $T^*\T^n$ with application to non convex   Hamiltonian systems
  In this paper, we show the existence of non contractible periodic orbits in Hamiltonian systems defined on $T^*\T^n$ separating two Lagrangian tori under certain cone assumption. Our result answers a question of Polterovich in \cite{P} in a sharp way. As an application, we find periodic orbits of almost all the homotopy types on a dense set of energy level in Lorentzian type mechanical Hamiltonian systems defined on $T^*\T^2$. This solves a problem of Arnold in \cite{A}. 
Jinxin Xue
math.DS math.SG