Controlled locally finite PL replacement #
This file packages the completed cellwise part of Moise Chapter 6, Theorem 3. The graph-level construction supplies quantitative face control and separation. Polygonal Schoenflies then fills every face, and local finiteness glues the fillings into a homeomorphism of supports.
The closed metric controls used for a replacement are contained in the permitted open region.
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- G.ControlsStayInRegion phi = ∀ (p : ↑K.support), Metric.closedBall (G.map p) (phi p) ⊆ G.region
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A global bound and a frontier-relative bound sufficient to control a locally finite family of polygonal face fillings.
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Frontier control keeps each selected polygonal disk inside the permitted open region.
The filled polygonal disks of a uniformly frontier-controlled replacement are locally finite in the open perturbation region. The proof confines any disk meeting a small ball to an original face meeting a fixed compact ball, then uses relative closed-embedding transport.
Convex target regions are preserved by the simultaneous polygonal replacement of the one-skeleton. The construction chooses each central broken line in the convex hull of its original embedded edge.
A source realization in the model half-plane has a replacement graph in that half-plane.
A zero-normal point of a complete replacement arc is supported by zero-normal points of the old embedded edge. This is the exact supporting-face statement behind boundary preservation; mere half-plane containment would only give one implication.
On the source one-skeleton, the assembled cellwise replacement is exactly the previously constructed global graph replacement.
The source zero-normal locus already lies in the source one-skeleton.
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On every source triangle, the supporting-line locus is an exposed face with at most two vertices. This is the intrinsic condition which excludes a boundary chord: the zero locus in a triangle is either empty, a vertex, or an entire edge.
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A facewise exposed zero locus is necessarily carried by the source one-skeleton.
The graph replacement preserves the zero-normal locus pointwise on its source graph.
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The exact edgewise alternatives needed at a supporting boundary line. On each old edge, the zero-normal locus is either the whole image, one incident vertex, or empty. In particular, this rules out an interior edge whose two endpoints lie on the model boundary while its interior does not: an arbitrary convex-hull polygonalization could otherwise create a spurious boundary segment.
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A facewise exposed zero locus gives the edgewise full/singleton/empty alternatives.
The edgewise zero-locus trichotomy makes the simultaneous graph replacement preserve the supporting boundary line exactly. The forward direction uses the supporting-face theorem for the replacement convex hull; the reverse direction uses vertex fixing in the singleton case.
The facewise exposed-face invariant is the single source-side hypothesis needed for exact zero-coordinate preservation by the simultaneous graph replacement.
Once exact zero-coordinate preservation is known on the replacement graph, the polygonal Schoenflies fillings preserve it on every filled face. No filled-face interior can reach the supporting line, so the two-dimensional statement reduces completely to the one-skeleton.
Exact preservation on filled faces, stated directly from the facewise exposed-face invariant.
A controlled compatible cellwise replacement lands in the permitted perturbation region.
The full locally finite Chapter 6 output from its quantitative graph hypotheses.
The complete locally finite Chapter 6 output in Moise's facewise side-control form. Uniform frontier control supplies target containment and local finiteness automatically.
The Chapter 6 cellwise approximation from the exact edge-mesh condition supplied by an internal edge subdivision. No independent side hypothesis remains: the incident-face minimum turns edgewise diameter control into the required facewise closeness.
If the replacement graph lies in the closed right half-plane, every selected polygonal face disk lies there too.
Consequently the entire assembled locally finite replacement complex stays in the closed right half-plane.
Pointwise half-plane preservation for the assembled replacement homeomorphism.