Rigidity properties of Anosov optical hypersurfaces
  We consider an optical hypersurface $\Sigma$ in the cotangent bundle $\tau:T^*M\to M$ of a closed manifold $M$ endowed with a twisted symplectic structure. We show that if the characteristic foliation of $\Sigma$ is Anosov, then a smooth 1-form $\theta$ on $M$ is exact if and only $\tau^*\theta$ has zero integral over every closed characteristic of $\Sigma$. This result is derived from a related theorem about magnetic flows which generalizes our work in \cite{DP}. Other rigidity issues are also discussed. 
Nurlan S. Dairbekov, Gabriel P. Paternain