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Mathlib.CategoryTheory.Abelian.Injective.Extend

Injective resolutions as cochain complexes indexed by the integers #

Given an injective resolution R of an object X in an abelian category C, we define R.cochainComplex : CochainComplex C ℤ, which is the extension of R.cocomplex : CochainComplex C ℕ, and the quasi-isomorphism R.ι' : (CochainComplex.singleFunctor C 0).obj X ⟶ R.cochainComplex.

If R : InjectiveResolution X, this is the cochain complex indexed by obtained by extending by zero the cochain complex R.cocomplex indexed by .

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    If R : InjectiveResolution X, then R.cochainComplex.X n (with n : ℕ) is isomorphic to R.cocomplex.X k (with k : ℕ) when k = n.

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      theorem CategoryTheory.InjectiveResolution.cochainComplex_d {C : Type u} [Category.{v, u} C] [Limits.HasZeroObject C] [Preadditive C] {X : C} (R : InjectiveResolution X) (n₁ n₂ : ) (k₁ k₂ : ) (h₁ : k₁ = n₁) (h₂ : k₂ = n₂) :
      R.cochainComplex.d n₁ n₂ = CategoryStruct.comp (R.cochainComplexXIso n₁ k₁ h₁).hom (CategoryStruct.comp (R.cocomplex.d k₁ k₂) (R.cochainComplexXIso n₂ k₂ h₂).inv)
      theorem CategoryTheory.InjectiveResolution.cochainComplex_d_assoc {C : Type u} [Category.{v, u} C] [Limits.HasZeroObject C] [Preadditive C] {X : C} (R : InjectiveResolution X) (n₁ n₂ : ) (k₁ k₂ : ) (h₁ : k₁ = n₁) (h₂ : k₂ = n₂) {Z : C} (h : R.cochainComplex.X n₂ Z) :

      The quasi-isomorphism (CochainComplex.singleFunctor C 0).obj X ⟶ R.cochainComplex in CochainComplex C ℤ when R is an injective resolution of X.

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        noncomputable def CategoryTheory.InjectiveResolution.Hom.hom' {C : Type u} [Category.{v, u} C] [Abelian C] {X : C} {R : InjectiveResolution X} {X' : C} {R' : InjectiveResolution X'} {f : X X'} (φ : R.Hom R' f) :

        The morphism on cochain complexes indexed by that is induced by an (heterogeneous) morphism of injective resolutions.

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          theorem CategoryTheory.InjectiveResolution.Hom.hom'_f {C : Type u} [Category.{v, u} C] [Abelian C] {X : C} {R : InjectiveResolution X} {X' : C} {R' : InjectiveResolution X'} {f : X X'} (φ : R.Hom R' f) (n : ) (m : ) (h : m = n) :
          theorem CategoryTheory.InjectiveResolution.Hom.hom'_f_assoc {C : Type u} [Category.{v, u} C] [Abelian C] {X : C} {R : InjectiveResolution X} {X' : C} {R' : InjectiveResolution X'} {f : X X'} (φ : R.Hom R' f) (n : ) (m : ) (h : m = n) {Z : C} (h✝ : R'.cochainComplex.X n Z) :