Alphabeta Math
RemarkRemark: AI-adaptedProof: Not applicable
How statement and proof provenance work

The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.

  • Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
  • AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
  • AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.

These labels describe origin, not correctness: citations and verification chips remain separate evidence.

Reeblessness and tautness are not equivalent without extra hypotheses

Statement

Assume ACω. For a smooth cooriented codimension-one foliation of a closed oriented three-manifold, tautness implies Reeblessness by A Reeb component obstructs tautness, but Reeblessness alone does not imply tautness.

Here is a closed example. On T3=(R/Z)3, with coordinates (x,y,z), put α=cos⁡(2πx) dx+sin⁡(2πx) dy. This is nowhere zero and α∧dα=0, so its kernel defines a smooth cooriented foliation by The codimension-one Frobenius criterion. The tori x=0 and x=1/2 are leaves. On each intervening strip the other leaves satisfy y+12πlog⁡∣sin⁡(2πx)∣=c(mod1), with z free, and are intrinsically cylinders. There are no plane leaves, so no saturated region can have the interior-plane foliation required by Reeb components of a codimension-one foliation. Thus the foliation is Reebless. The compact saturated region 0≤x≤1/2 has the α-positive normal pointing inward at both boundary tori. It is a dead-end component in Dead-end components, so the foliation is not taut by A foliation is taut if and only if it has no dead-end component.

Remarks

Ranz, Corollary 2.13(ii), printed pp.40–41, instead describes a noncompact strip product. Its strips are not compact dead-end components under this page's definition, so that terminology does not justify the closed-manifold comparison. The explicit torus construction above supplies the witness directly. The single-transversal conclusion additionally uses nonempty compact connected ambient manifolds, as stated in A taut foliation of a compact connected manifold has a single closed transversal.

Depends on

Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

41 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.

Sources