Dual normalization on the standard-form universal cover #
The positive-height construction normalizes realized sinks. This file implements the dual induction on arrows whose module-theoretic source has nonpositive Bongartz--Gabriel height. It normalizes realized sources while retaining their minimal left almost-split invariant.
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A lifted standard-form vertex whose represented module is noninjective.
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Polarization commutes with transport of its nonprojective mesh endpoint.
The inverse polarization also commutes with transport of its nonprojective mesh endpoint.
Extract a component from a replacement source at one downstairs noninjective standard-form vertex.
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On a polarized displayed occurrence, downstairs source-component extraction is literal postcomposition with the middle projection.
Extract from a replacement mesh source the component represented by one arrow ending at the translated vertex.
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Component extraction recovers the indicated component on each explicit polarized middle arrow.
Source-component extraction is invariant under simultaneous transport of the lifted mesh endpoint and its outgoing arrow.
For an arrow whose represented module source is noninjective, recover the downstairs endpoint of the right mesh that produces it by polarization.
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The recovered downstairs mesh endpoint translates to the arrow target's base label.
The downstairs polarized partner of an arrow ending at a noninjective lifted vertex.
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Lift the recovered downstairs polarized partner into the costar of the arrow's source vertex. This determines the unique lifted mesh containing the arrow.
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Projecting the recovered costar lift returns its defining downstairs polarized partner.
The nonprojective lifted mesh endpoint recovered from an arrow ending at a noninjective vertex.
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The lifted polarized partner from the recovered mesh endpoint to the original arrow's source vertex.
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The recovered mesh endpoint and arrow are exactly the costar lift constructed above.
The recovered lifted mesh endpoint lies over its recovered downstairs endpoint.
After the base-label transport, the recovered lifted arrow projects to the recovered downstairs polarized partner.
Pairing the recovered mesh arrow returns the original universal-cover arrow, including its target vertex.
The translated source vertex of every universal mesh represents a noninjective module.
Applied to an explicit polarized mesh arrow, the recovered costar is the original lifted middle arrow.
Applied to an explicit polarized mesh arrow, source-mesh recovery returns the original lifted mesh endpoint.
Simultaneously replace source components on all arrows whose represented module source has one fixed height. Injective sources are left unchanged; every other arrow canonically recovers its unique lifted mesh.
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At a selected mesh source height, simultaneous source replacement returns the supplied component on every displayed paired arrow.
Target-height replacement leaves an arrow unchanged away from the selected target height.
Target-height replacement also leaves arrows ending at injective vertices unchanged.
At the selected translated-source height, the source assembled from all replaced components is exactly the supplied source.
Away from the selected translated-source height, target-height replacement leaves the realized mesh source unchanged.
A component cut out by a split projection from a minimal left almost-split morphism between selected indecomposables is irreducible.
The global invariant used by the descending source normalization.
- arrow_isIrreducible {Y Z : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀} (a : Y ⟶ Z) : QuotientSubmoduleEquidistribution.IsIrreducibleMorphism (D a)
- leftAlmostSplit (W : { W : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀ // W ∉ MeshCategory.RightMeshData.UniversalCover.projectiveSet S.standardFormRightMeshData x₀ }) : QuotientSubmoduleEquidistribution.IsLeftAlmostSplit (S.standardFormUniversalRealizedSource x₀ (fun {W Z : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀} => D) W)
- leftMinimal (W : { W : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀ // W ∉ MeshCategory.RightMeshData.UniversalCover.projectiveSet S.standardFormRightMeshData x₀ }) : QuotientSubmoduleEquidistribution.IsLeftMinimal (S.standardFormUniversalRealizedSource x₀ (fun {W Z : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀} => D) W)
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The positive limiting assignment supplies the initial invariant for the descending source normalization.
Under the global source invariant, each realized sink differs from the chosen right almost-split sink by an automorphism of the displayed middle term.
The canonical comparison automorphism between the chosen mesh sink and the sink assembled from a source-compatible assignment.
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The comparison automorphism realizes the assembled sink exactly.
Every sink assembled from a source-compatible assignment is right almost split, including the projective boundary vertices.
Twist the chosen mesh source by the inverse sink comparison.
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The normalized source has zero composite with the currently realized sink.
The normalized source has zero composite with the currently realized sink.
The normalized source remains left almost split.
The normalized source remains left minimal.
Precomposition by equality transport preserves irreducibility.
Postcomposition by equality transport preserves irreducibility.
Every component extracted from the normalized source is irreducible.
The replacement source used at one translated-source height.
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Simultaneously normalize all mesh sources whose translated vertex has one fixed height.
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Replacing sources at translated height m does not alter the realized
sink in the same mesh: its outgoing arrows end at height m + 1.
One target-height normalization preserves irreducibility and the global minimal left almost-split source invariant.
Every mesh at the selected translated-source height satisfies its literal zero relation after simultaneous source normalization.
An arrow assignment together with the global source invariant required by the descending induction.
- arrowMap : S.StandardFormUniversalArrowAssignment x₀
- sourceCondition : S.StandardFormUniversalSourceCondition x₀ fun {W Z : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀} => self.arrowMap
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The positive limiting assignment is the initial state of the descending source induction.
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Normalize all sources at one translated-source height while retaining the global source invariant.
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Stage n + 1 of the descending induction normalizes translated-source
height -n; stage zero is the positive limiting assignment.
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A successor descending stage changes only arrows whose target has the newly processed height.
Positive-target arrows are never changed by the descending induction.
Once target height -n has been processed, all later descending stages
agree on arrows with that target height.
The two-sided limiting assignment: nonpositive arrow targets use their stabilized descending stage; positive targets retain the positive limit.
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At target height -n, the two-sided limit agrees with descending stage
n + 1.
At positive target height, the two-sided limit agrees with the positive limiting assignment.
For a mesh whose translated source has height -n, its source in the
two-sided limit is already its source at stage n + 1.
For a mesh whose translated source has height -n, its sink in the
two-sided limit is also already its sink at stage n + 1.
Every mesh whose translated source has height -n satisfies its literal
zero relation in the two-sided limiting assignment.
Every representative in the two-sided limiting assignment remains irreducible.
Every lifted mesh satisfies its literal zero relation in the two-sided limiting assignment.