a1 Department of Mathematics, Keio University, Yokohama 223, Japan
We are concerned with closed C∞ riemannian manifolds of negative curvature whose geodesic flows have C∞ stable and unstable foliations. In particular, we show that the geodesic flow of such a manifold is isomorphic to that of a certain closed riemannian manifold of constant negative curvature if the dimension of the manifold is greater than two and if the sectional curvature lies between −and −1 strictly.
(Received April 02 1987)
(Revised August 20 1987)
† Dedicated to Professor Morio Obata on his 60th birthday.