Variations d'entropies et déformations de structures conformes plates sur les variétés hyperboliques compactes

We study the link between variations of entropy on a compact hyperbolic manifold $M$ and infinitesimal flat conformal deformations of $M$. We remark that the entropy of the Liouville measure increases in the direction of these deformations. We then explain a new construction of infinitesimal flat conformal deformations by bending along totally geodesic hypersurfaces of $M$ which allows us to extend a theorem of L. Flaminio.

Hyperbolic behaviour of geodesic flows on manifolds with no focal points

It is shown that the unit tangent bundle of a compact uniform visibility manifold with no focal points contains a subset of positive Liouville measure on which all the characteristic exponents of the geodesic flow (except in the flow direction) are non-zero. This completes Pesin's proof that the geodesic flow of such a manifold is Bernoulli.