The Livšic equation on differential forms over Anosov flows and applications
Slobodan N. Simić
TL;DR
The paper develops a Livšic-type theory for the Lie derivative $L_X$ of differential forms along an Anosov flow on a closed manifold, focusing on the solvability of $L_X\xi=\eta$ across form degrees. It proves a sharp existence and uniqueness result for intermediate degrees $2\le k \le n-2$ in the asymmetric codimension-one setting, and links the $L^2$-closure of the image of $L_X$ on $(n-1)$-forms to a geometric integrability condition: the sum of the strong bundles is uniquely integrable, which implies a topological conjugacy to a suspension of an Anosov diffeomorphism. The work uses elementary, non-mmicrolocal methods together with the Gol'dshtein–Troyanov complex to study regularization, cohomology, and duality, connecting dynamical rigidity to differential-form cohomology. The results provide a criterion tying dynamical geometric structure to the solvability of cohomological equations and to global cross-section-type behavior of the flow. The findings have implications for understanding when asymmetric Anosov flows admit suspension representations and illuminate the relationship between flow geometry and analytic properties of $L_X$ on differential forms.
Abstract
The goal of this paper is to explore the relationship between the geometric properties of an Anosov flow on a closed manifold $M$ and the analytic properties of its infinitesimal generator $X$ as a linear operator on the space of smooth differential forms of all degrees. In particular, we study the solvability of the Livšic equation $L_X ξ= η$ on the space of differential forms and show, for instance, that if the Anosov flow is \emph{asymmetric}, then the equation has a unique solution in the continuous category in degrees $2 \leq k \leq n-2$, where $n = \dim M$. Intuitively, an Anosov flow is asymmetric if in negative time it shrinks the volume of any $(n-2)$-dimensional parallelepiped exponentially fast when at least one side of it is in the strong unstable direction. As an application, we show that for volume-preserving asymmetric Anosov flows, the following result holds: the $L^2$-closure of the image of $L_X$ restricted to differential forms of degree $(n-1)$ contains the space of $L^2$-exact $(n-1)$-forms if and only if the sum of the strong bundles of the flow is uniquely integrable, in which case the flow is therefore topologically conjugate to a suspension of an Anosov diffeomorphism.
