The literal primitive-deletion layer #
For a primitive idempotent e, the indecomposable modules over A / AeA
are already present in the ambient skeleton: they are exactly the labels on
which AeA acts by zero. This file records that identification at the level
needed by the new-mesh/new-arrow argument and fixes one ambient
Krull--Schmidt multiplicity function for all subsequent counts.
No second quotient-only counting model is introduced. In particular, the multiplicity of a summand in a Hoshino torsion middle term is measured by the same ambient skeleton that defines the ambient arrow multiplicities.
The ambient skeleton labels which are literal indecomposables over the
primitive quotient A / AeA.
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A primitive-quotient label, bundled in the full subcategory of ambient
modules annihilated by AeA.
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The deleted simple E = S_e, realized as the top of its primitive
projective cover.
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The canonical projective-cover map onto the deleted simple.
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The deleted simple maps one-dimensionally into the distinguished primitive injective.
A chosen nonzero embedding of the deleted simple into its distinguished primitive injective.
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The chosen map from the deleted simple to the primitive injective is nonzero.
The chosen nonzero map from the simple E is monic.
Every map from a killed additive object to the deleted simple is zero.
There are no maps from the deleted simple to an indecomposable module
over A/AeA.
Every map from the deleted simple to a killed additive object is zero.
For an idempotent generator, the full subcategory annihilated by AeA
is extension closed.
Every displayed ambient decomposition of an AeA-annihilated module
uses only primitive-quotient labels.
Hence every AeA-annihilated module belongs to the additive closure of
the primitive-quotient labels in the ambient skeleton.
The ambient decomposition chosen by the tau-category construction also uses only primitive-quotient labels on an annihilated module.
Multiplicity of one ambient skeleton label in the fixed displayed Krull--Schmidt decomposition of a finitely generated module.
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The fixed multiplicity agrees with the occurrence count in any other displayed decomposition into the same ambient skeleton.
The fixed multiplicity agrees with a decomposition indexed by any finite
type. This is the index-neutral form used by almost-split decompositions,
whose index is stored as a FintypeCat.
Ambient indecomposable multiplicity is invariant under module isomorphism.
Ambient indecomposable multiplicity is additive across a binary biproduct.
The multiplicity of a skeleton label in one displayed indecomposable is the corresponding Kronecker delta.
At every ambient endpoint, including the projective boundary, the fixed object multiplicity of the standard right-mesh middle term is exactly the ambient arrow multiplicity.
A label outside the primitive quotient has multiplicity zero in every
AeA-annihilated module.
Every Hoshino torsion radical decomposes entirely into literal primitive-quotient labels.
Consequently, labels deleted from the literal quotient never occur in a Hoshino torsion middle term.
The ambient Auslander--Reiten sequence at an arbitrary nonprojective selected label, with its kernel identified with the selected translate.
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Every displayed ambient Auslander--Reiten sequence is short exact.
A right endpoint whose relative Auslander--Reiten mesh is new after
primitive deletion. Its endpoint is an A/AeA-module, it is
nonprojective in that literal quotient category, and its ambient translate
lies outside the quotient subcategory.
- label : S.PrimitiveQuotientLabel D
- quotient_nonprojective : ¬CategoryTheory.Projective (S.primitiveQuotientLabelObj D self.label)
- translation_not_mem : S.rightTranslationLabel ⟨↑self.label, ⋯⟩ ∉ S.primitiveKilledLabels D
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The endpoint as an ambient nonprojective label.
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The deleted ambient translate q_N = τ_A N, bundled as a surviving
label of the factor category mod A / [mod (A/AeA)].
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The marker q_N = τ_A N is tau-injective in the factor category: its
ambient inverse translate is the quotient label N, which is killed in the
factor.
The factor-injective boundary label supplied by a new mesh endpoint.
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The boundary coordinate theorem gives the marker multiplicity
[q_N : S_e] = 1.
The manuscript's positive boundary test, expressed in the form used by
the new-arrow construction: Hom_A(S_e,q_N)=0. Complementarity with the
left marker is proved at the later boundary-correspondence layer.
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At a positive new mesh, the deleted simple has no map to the ambient AR middle term.
The Hoshino torsion radical of the ambient translate is the source of the new relative mesh.
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The middle term of the new relative mesh is the torsion radical of the ambient right almost-split middle term.
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Ambient injectivity of the transported AR-kernel inclusion.
The ambient FG-module short complex underlying the new relative mesh.
Its terms are R(τ_A N), R(V_N), and N.
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Hoshino's comparison makes the displayed new relative mesh short exact.
The Hoshino torsion kernel which starts the new relative mesh is not injective even in the ambient module category.
The source label selected from Hoshino's indecomposable torsion radical.
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The selected source label represents the actual torsion kernel
R(τ_A N).
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The source of a new relative mesh is itself a literal
A/AeA-indecomposable.
The selected ambient source label is noninjective.
The source M of the new relative mesh, bundled in the same literal
quotient label type as its endpoint N.
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The source M as an ambient noninjective label, so that its inverse
Auslander--Reiten translate is defined.
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The ambient inverse-translation label underlying the manuscript's left
marker p_M = τ_A⁻¹M. The later boundary theorem proves that it lies
outside the primitive quotient label set.
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Relative arrow multiplicity into N, computed in the existing ambient
skeleton from the Hoshino torsion middle term.