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A paired immersed cap sweep excludes a positive closed transversal
Statement
For a coherent regular cap family with simple lifted boundaries, an infinite center track, fixed-flow fence, no-hit neighborhood and recurrent nested source disks, the reduced essential initial leaf meets no positive closed transversal.
Facts & Assumptions
Given: A coherent regular cap family with simple lifted boundaries, an infinite centre track, a fixed-flow fence, a no-hit neighbourhood and recurrent nested source disks.
The in-pair item Common plaque lifted caps admit nested source-disk inclusions supplies the nested source-disk inclusions and paired base gluing maps; the in-pair item A paired regular disk sweep is open across its base gluing supplies the local seam openness of the paired quotient; the in-pair item The canonical Jordan cap bundle develops coherently over every positive band supplies the regular cap development and its lifted Jordan disks; the in-pair item Compact leaves near a compact reference leaf are one-sheeted collar graphs supplies open transversal saturation; Fixed transverse fences and their finite crossing words supplies the fixed-flow fence and finite crossing word.
The sibling-pair items lem-fixed-transverse-fences-have-a-finite-crossing-word and lem-finite-chart-surface-normal-forms-supply-jordan-disks-and-torsion-free-groups supply the finite fence data and the surface-Jordan disk together with the finite interval-chart cancellation of a compact oriented one-manifold; their uses are flagged in steps 1.1 and 7.1 below.
The standing assumption is Countable Choice as recorded for this pair (The countable-choice principle used in the foliation pair).
Proof
For contradiction suppose a positive closed transversal meets the reduced initial leaf. Move one crossing to a regular point of its essential loop using Positive transverse accessibility is a preorder. Put , the compact loop image. The intersections of this transversal with are isolated: in a foliation box the transversal has strictly monotone transverse coordinate while each local branch lies in a plaque, so compactness and finitely many local branches give finitely many intersections after a small positive perturbation avoiding passage through double points. Choose disjoint parameter intervals for all intersections other than the selected regular point and small boxes in which each branch is an embedded arc in one plaque; in box coordinates replace the transversal by a small tangentially shifted arc near each crossing, interpolating to the original arc on end collars, with the tangential shift chosen transverse to the one-dimensional branch in the two-dimensional plaque. It misses that branch, the transverse-coordinate derivative stays positive because only tangential coordinates change, and shrinking each box excludes all other branches, interpolating at transverse levels separated from the branch plaques so that no new intersections appear; finite gluing retains regularity and positivity. At keep an interval fixed, and note that the remainder outside a slightly larger -box is compact and disjoint from , hence has positive ambient distance from for this fixed box and transversal.
Choose a small box around so that the initial loop meets in one embedded arc with every other boundary parameter outside a larger closed box; uniform continuity of the short fence keeps those other parameters outside at all sufficiently small levels. In each plaque met by the boundary, its sole boundary arc is close to the initial regular arc, so a fixed smaller plaque rectangle is split into two connected half-rectangles by that arc, with one uniform tangential and normal size. Lift to the universal cover of the leaf at that boundary point; the component of the plaque rectangle through the chosen lift maps diffeomorphically to its plaque rectangle, and the Jordan boundary has no other boundary points in this lifted rectangle because all other projected boundary parameters avoid . Its disk side contains one local half-neighbourhood by the boundary collar, and membership in the Jordan interior cannot change along a path in the corresponding half-rectangle without crossing the boundary, so the entire chosen half-rectangle lies in the disk. Leaf orientation identifies the selected side with the sign of the boundary orientation, which is constant on any connected interval with compact cap transport.
Suppose a positive closed transversal meets the reduced initial leaf. Finite leaf-path transport and positive perturbation move a crossing to a regular point of the essential loop , away from its finitely many double points, and tangential perturbations in finitely many foliation boxes remove its other intersections with as in step 1.1. In a fixed- flowbox near write coordinates with -orbits vertical and an embedded arc in ; replace the local transversal, preserving its positive transverse derivative and its end collars, by near , where is a small vector pointing into the selected local cap half-plaque. For sufficiently small its basepoint lies off ; since the whole normal fence consists of -orbits over , this local transversal misses the entire positive fence, and the compact remainder of has positive distance from , so after shrinking the fence it also misses the fence. Hence is disjoint from the entire lateral boundary of every sufficiently late paired sweep while still crossing on the inward side.
Fix a late upper cap and choose the lower recurrent cap so late that is included in it by the source-disk inclusion and that a fixed small neighbourhood of disjoint from the compact image of contains near . In that box the cap contains the uniform local plaque half-neighbourhood of step 2.1. The local leaf plaque is a graph with and tending to ; transversality and small make strictly increasing, so it has a small positive zero . At this point crosses the plaque on its selected interior side because its tangential displacement is inward, and the crossing lies outside the image of , so it belongs to the unglued -base annulus . Thus meets and misses and the boundary seams.
The paired quotient is an oriented compact three-manifold with boundary : identifying the whole -base disk with the interior source disk of the -base identifies two boundary disks of the original three-ball, local disk collars give manifold charts across the identified bases, and the boundary is the remaining -base annulus together with the lateral annulus. The seam lemma of [F1] strengthens to a local orientation-preserving homeomorphism in the interior, since the two half-charts map injectively to opposite sides of their common plaque and agree on it, while other interior charts are regular local diffeomorphisms. Along the positive transverse direction points inward to , because this -base has available cylinder side and the sweep is negatively transverse.
Form the fibre product . It is closed in the compact product, hence compact. Interior local homeomorphism charts of identify locally with an interval of the oriented transversal, the piecewise seam causing no topological defect; along transversality gives half-interval charts; there are no points over or the boundary corners because misses their images. Therefore is a compact oriented one-manifold with boundary, and its boundary is nonempty by the crossing of step 4.1. At every boundary point the positive direction enters , so every boundary point has the same boundary sign, which is impossible because a compact oriented one-manifold has zero total signed boundary: choose a finite oriented interval-chart cover, subdivide into finitely many short intervals subordinate to it, and cancel the paired internal endpoints, each interval contributing one positive and one negative endpoint. This contradiction shows that the reduced leaf meets no closed positive transversal.
The argument uses multiple-sheet preimages with their multiplicities and never identifies an immersed cap image with an embedded region, and it consumes only the finitely many boxes, source disks and the fibre product, hence only the standing countable choice from [F3].
Depends on
- The countable-choice principle used in the foliation pair
- Common plaque lifted caps admit nested source-disk inclusions
- A paired regular disk sweep is open across its base gluing
- Compact leaves near a compact reference leaf are one-sheeted collar graphs
- Fixed transverse fences and their finite crossing words
- Finite surface normal forms, Jordan disks, and torsion control
- The canonical Jordan cap bundle develops coherently over every positive band
- Positive transverse accessibility is a preorder
Used by
Dependency tree · two levels
58 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
- S. P. Novikov, The Topology of Foliations (complete English translation) (standard reference, not scraped)
- Mark Brittenham, Foliations and the Topology of 3-Manifolds, classes 11-20 (standard reference, not scraped)