Numerical invariants — Question 13.4

Definitions and mathematical statement

Shared notation.

$\mathbb N=\{1,2,\ldots\}$, and $\mathbb Z,\mathbb Q,\mathbb R,\mathbb C$ denote the integers, rationals, reals and complex numbers. Any other conventions are specified locally.

A codimension-one foliation $\mathcal F$ decomposes a $3$-manifold $M$ into surface leaves, locally as the horizontal slices of a product chart. In the terminology of the source, it is taut if a closed curve transverse to $\mathcal F$ meets every leaf. A minimal foliation means that every leaf is dense; a minimal surface means a surface with vanishing mean curvature for the specified Riemannian metric. These two uses of minimal are distinct.

Statement recorded in the supplied source.

Find hyperbolic $M$ with taut foliations $\mathcal F,\mathcal G$ and a finite covering $p:\widehat M\to M$ such that there are ambient isotopies upstairs whose terminal maps $h_i$ satisfy $(h_i)_*(p^*\mathcal G)\to p^*\mathcal F$ geometrically, whereas no sequence of terminal maps of ambient isotopies downstairs takes $\mathcal G$ geometrically to $\mathcal F$. The convergence is local geometric convergence of the foliated structures; the upstairs isotopies need not descend. [S2]

Short English statement

Can geometric degeneration of one taut foliation to another become possible in a finite cover when it is impossible on the original manifold?

Sources

• S1 ULAM.AI and the UnsolvedMath Contributors, UnsolvedMath: A Curated Collection of Open Mathematics Problems, record 10300057 (AMR-102-0057). CC BY 4.0. https://huggingface.co/datasets/ulamai/UnsolvedMath.
• S2 Danny Calegari, Problems in foliations and laminations of 3-manifolds, version 0.78 (2002), Question 13.4; Definitions 1.1--1.10 and local definitions and remarks. https://arxiv.org/abs/math/0209081v1.