Entropy expansiveness of geodesic flows on closed manifolds without conjugate points
In this article, we consider the entropy expansiveness of geodesic flows on closed Riemannian manifolds without conjugate points. We prove that, if the manifold has no focal points, or if the manifold is bounded asymptote, then the geodesic flow is entropy expansive. Moreover, for the compact oriented surfaces without conjugate points, we prove that the geodesic flows are entropy expansive. We also give an estimation of distance between two positively asymptotic geodesics of an uniform visibility manifold.