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Mathlib.GroupTheory.FiniteAbelian

Structure of finite(ly generated) abelian groups #

theorem AddCommGroup.equiv_free_prod_directSum_zmod (G : Type u) [AddCommGroup G] [hG : AddGroup.FG G] :
∃ (n : ) (ι : Type) (x : Fintype ι) (p : ι) (_ : ∀ (i : ι), Nat.Prime (p i)) (e : ι), Nonempty (G ≃+ (Fin n →₀ ) × DirectSum ι fun (i : ι) => ZMod (p i ^ e i))

Structure theorem of finitely generated abelian groups : Any finitely generated abelian group is the product of a power of and a direct sum of some ZMod (p i ^ e i) for some prime powers p i ^ e i.

theorem AddCommGroup.equiv_directSum_zmod_of_fintype (G : Type u) [AddCommGroup G] [Finite G] :
∃ (ι : Type) (x : Fintype ι) (p : ι) (_ : ∀ (i : ι), Nat.Prime (p i)) (e : ι), Nonempty (G ≃+ DirectSum ι fun (i : ι) => ZMod (p i ^ e i))

Structure theorem of finite abelian groups : Any finite abelian group is a direct sum of some ZMod (p i ^ e i) for some prime powers p i ^ e i.