Simple-module counts under algebra equivalence #
theorem
MagnitudeConjecture.RightModule.FiniteIndecomposableSkeleton.simpleCount_mapAlgEquiv
{k A B : Type u}
[Field k]
[Ring A]
[Algebra k A]
[FiniteDimensional k A]
[IsNoetherianRing Aᵐᵒᵖ]
[Ring B]
[Algebra k B]
[FiniteDimensional k B]
[IsNoetherianRing Bᵐᵒᵖ]
(S : FiniteIndecomposableSkeleton k A)
(f : A ≃ₐ[k] B)
:
(S.mapAlgEquiv f).simpleCount = S.simpleCount
Transporting the complete family along an algebra equivalence preserves the literal number of simple-module classes.