Laurent Stolovitch (Université Côte d’Azur)
In this article, we consider perturbations of isometries on a compact Riemannian manifold $M$.
We investigate the smooth (resp. analytic) rigidity phenomenon of groups of these isometries. As a particular case, we prove that if a finite family of smooth (resp. analytic) small enough perturbations is simultaneously conjugate to the family of isometries via a finitely smooth diffeomorphism, then it is simultaneously smoothly (resp. analytically) conjugate to it whenever the family of isometries satisfies a Diophantine condition.
Our results generalize the rigidity theorems of Arnold, Herman, Yoccoz, Moser, etc. about circle diffeomorphisms which are small perturbations of rotations as well as Fisher-Margulis’s theorem on group actions satisfying Kazhdan’s property (T). This a collaboration with Zhiyan Zhao.