The canonical lamination calibrated by a cohomology class
Aidan Backus
TL;DR
The paper constructs a canonical lamination $\lambda_\rho$ calibrated by every calibration in a unit-norm cohomology class $\rho\in H^{d-1}(M,\mathbb{R})$ on a closed oriented manifold $M$ with $2\le d\le 7$, showing its leaves are minimal hypersurfaces calibrated in $\rho$. It establishes a deep duality between calibrations and laminations, tying the geometry of $\lambda_\rho$ to the unit ball of the stable norm and introducing an earthquake-norm analogue in this infinitesimal setting. By developing the BV/least-gradient framework and ergodic theory of transverse measures, the authors prove that the dual flat $\rho^*$ is a polytope whose rational vertices correspond to closed leaves, and they provide bounds on irrational vertices via the first Betti number; they also derive strict convexity criteria linked to the fundamental group’s derived series, implying abundant uniquely ergodic calibrated laminations under topological constraints. The work draws a conceptual bridge to Teichmüller theory, offering a calculus of calibrations and laminations that constrains stable-norm geometry and hints at higher-dimensional extensions and singularity phenomena beyond $d=7$.
Abstract
Let $M$ be a closed oriented Riemannian manifold of dimension $2 \leq d \leq 7$, and let $ρ\in H^{d - 1}(M, \mathbb R)$ have unit norm. We construct a lamination $λ_ρ$ whose leaves are exactly the minimal hypersurfaces which are calibrated by every calibration in $ρ$. The geometry of $λ_ρ$ is closely related to the the geometry of the unit ball of the stable norm on $H_{d - 1}(M, \mathbb R)$, and so we deduce several results constraining the geometry of the stable norm ball in terms of the topology of $M$. These results establish a close analogy between the stable norm on $H_{d - 1}(M, \mathbb R)$ and the earthquake norm on the tangent space to Teichmüller space.
