Topological invariance of Liouville structures for taut foliations and Anosov flows

Abstract

Building on the work of Eliashberg and Thurston, we associate to a taut foliation on a closed oriented $3$-manifold $M$ a Liouville structure on the thickening $[-1,1] \times M$, under suitable hypotheses. Our main result shows that this Liouville structure is a topological invariant of the foliation: two such foliations which are topologically conjugate induce Liouville structures that are exact symplectomorphic (after completion). Specializing to the case of weak foliations of Anosov flows, we obtain that under natural orientability conditions, the Liouville structures originally introduced by Mitsumatsu are invariant under orbit equivalence. Our methods also imply that two orbit equivalent Anosov flows are deformation equivalent through projectively Anosov flows. The proofs combine two main technical ingredients: (1) a careful smoothing scheme for topological conjugacies between $C^1$-foliations, and (2) a refinement of a deep result of Vogel on the uniqueness of contact structures approximating a foliation. In an appendix, this smoothing scheme is used to construct new examples of collapsed Anosov flows, providing a key step to complete the classification of transitive partially hyperbolic diffeomorphisms in dimension three.