Primitive-coordinate boundary bounds from finite kernels #
theorem
MagnitudeConjecture.RightModule.FiniteIndecomposableSkeleton.primitiveMultiplicity_rightTranslation_le_one_of_killed_finiteKernel
{k A : Type u}
[Field k]
[Ring A]
[Algebra k A]
[FiniteDimensional k A]
[IsNoetherianRing Aᵐᵒᵖ]
[IsAlgClosed k]
(S : FiniteIndecomposableSkeleton k A)
(H : S.HasAcyclicNonzeroNonisomorphisms)
{e : A}
(D : PrimitiveIdempotentData e)
(z : { z : Fin S.n // ¬CategoryTheory.Projective (S.fgObj z) })
(hz : ↑z ∈ S.primitiveKilledLabels D)
:
S.primitiveMultiplicity D (S.rightTranslationLabel z) ≤ 1
If the last term of an almost-split sequence is killed by e, its first term has primitive-coordinate dimension at most one.
theorem
MagnitudeConjecture.RightModule.FiniteIndecomposableSkeleton.primitiveMultiplicity_injective_le_one_finiteKernel
{k A : Type u}
[Field k]
[Ring A]
[Algebra k A]
[FiniteDimensional k A]
[IsNoetherianRing Aᵐᵒᵖ]
[IsAlgClosed k]
(S : FiniteIndecomposableSkeleton k A)
(H : S.HasAcyclicNonzeroNonisomorphisms)
{e : A}
(D : PrimitiveIdempotentData e)
(z : Fin S.n)
[CategoryTheory.Injective (S.fgObj z)]
:
S.primitiveMultiplicity D z ≤ 1
Every indecomposable injective has primitive-coordinate dimension at most one, by the finite-kernel argument.