Transitive centralizers and fibered partially hyperbolic systems

Abstract

We prove several rigidity results about the centralizer of a smooth diffeomorphism, concentrating on two families of examples: diffeomorphisms with transitive centralizer, and perturbations of isometric extensions of Anosov diffeomorphisms of nilmanifolds. We classify all smooth diffeomorphisms with transitive centralizer: they are exactly the maps that preserve a principal fiber bundle structure, acting minimally on the fibers and trivially on the base. We also show that for any smooth, accessible isometric extension $f_0:M\to M$ of an Anosov diffeomorphism of a nilmanifold, subject to a spectral bunching condition, any $f\in {\mathrm{Diff}}^{\infty }(M)$ sufficiently $C^1$-close to $f_0$ has centralizer a Lie group. If the dimension of this Lie group equals the dimension of the fiber, then $f$ is a principal fiber bundle morphism covering an Anosov diffeomorphism. Using the results of this paper, we further classify the centralizer of any partially hyperbolic diffeomorphism on a $3$-dimensional, nontoral nilmanifold: either the centralizer is virtually trivial, or the diffeomorphism is an isometric extension of an Anosov diffeomorphism, and the centralizer is virtually $\mathbb{Z}\times \mathbb{T}$.

We add a global centralizer rigidity classification result for arbitrary partially hyperbolic diffeomorphisms on 3 dimensional non-toral nilmanifolds, see Theorem 3. The abstract and introduction are also updated