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fix(RingTheory): correct misnamed theorem (#39741)
Update `isFinitelyPresented` to `finitePresentation` to match the typeclass `Module.FinitePresentation`.
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Mathlib/RingTheory/Flat/EquationalCriterion.lean

Lines changed: 7 additions & 4 deletions
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@@ -44,7 +44,7 @@ that $x = y \circ a$ and $a \circ f = 0$. We recover the usual equational criter
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$K = R$ and $N = R^l$. This is used in the proof of Lazard's theorem.
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We conclude that every linear map from a finitely presented module to a flat module factors
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through a finite free module (`Module.Flat.exists_factorization_of_isFinitelyPresented`), and
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through a finite free module (`Module.Flat.exists_factorization_of_finitePresentation`), and
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every finitely presented flat module is projective (`Module.Flat.projective_of_finitePresentation`).
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## References
@@ -268,9 +268,9 @@ theorem exists_factorization_of_comp_eq_zero_of_free [Flat R M] {K N : Type*} [A
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/-- Every homomorphism from a finitely presented module to a flat module factors through a finite
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free module. -/
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@[stacks 058E "only if"]
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theorem exists_factorization_of_isFinitelyPresented [Flat R M] {P : Type*} [AddCommGroup P]
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theorem exists_factorization_of_finitePresentation [Flat R M] {P : Type*} [AddCommGroup P]
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[Module R P] [FinitePresentation R P] (h₁ : P →ₗ[R] M) :
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∃ (k : ℕ) (h₂ : P →ₗ[R] (Fin k →₀ R)) (h₃ : (Fin k →₀ R) →ₗ[R] M), h₁ = h₃ ∘ₗ h₂ := by
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∃ (k : ℕ) (h₂ : P →ₗ[R] (Fin k →₀ R)) (h₃ : (Fin k →₀ R) →ₗ[R] M), h₁ = h₃ ∘ₗ h₂ := by
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have ⟨_, K, ϕ, hK⟩ := FinitePresentation.exists_fin R P
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haveI : Module.Finite R K := .of_fg hK
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have : (h₁ ∘ₗ ϕ.symm ∘ₗ K.mkQ) ∘ₗ K.subtype = 0 := by
@@ -281,9 +281,12 @@ theorem exists_factorization_of_isFinitelyPresented [Flat R M] {P : Type*} [AddC
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apply (cancel_right K.mkQ_surjective).mp
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simpa [comp_assoc]
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@[deprecated (since := "2026-05-23")]
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alias exists_factorization_of_isFinitelyPresented := exists_factorization_of_finitePresentation
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@[stacks 00NX "(1) → (2)"]
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theorem projective_of_finitePresentation [Flat R M] [FinitePresentation R M] : Projective R M :=
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have ⟨_, f, g, eq⟩ := exists_factorization_of_isFinitelyPresented (.id (R := R) (M := M))
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have ⟨_, f, g, eq⟩ := exists_factorization_of_finitePresentation (.id (R := R) (M := M))
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.of_split f g eq.symm
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end Module.Flat

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