Irreducible short exact sequences in a finite module category #
A complete finite indecomposable skeleton supplies a chosen minimal right almost-split map at every indecomposable endpoint. Consequently the abstract irreducible-short-exact comparison theorem can be applied without making the comparison sequence an extra input.
theorem
MagnitudeConjecture.CoveringHom.FiniteDimensionalModuleIndecomposableSkeleton.isRightAlmostSplit_of_shortExact_of_irreducible
{k : Type uK}
[Field k]
{C : Type u}
[CategoryTheory.Category.{v, u} C]
[CategoryTheory.Preadditive C]
[CategoryTheory.Linear k C]
(V : FiniteDimensionalModuleIndecomposableSkeleton)
[CategoryTheory.EnoughProjectives (FiniteDimensionalModuleCategory k)]
{S : CategoryTheory.ShortComplex (FiniteDimensionalModuleCategory k)}
(hS : S.ShortExact)
(hf : QuotientSubmoduleEquidistribution.IsIrreducibleMorphism S.f)
(hg : QuotientSubmoduleEquidistribution.IsIrreducibleMorphism S.g)
(y : Fin V.n)
(eā : S.Xā ā
V.obj y)
:
A short exact complex with two irreducible differentials and an endpoint in a complete finite indecomposable skeleton is right almost split.