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Mathlib.Algebra.Homology.Additive

Homology is an additive functor #

When V is preadditive, HomologicalComplex V c is also preadditive, and homologyFunctor is additive.

TODO: similarly for R-linear.

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  • HomologicalComplex.instZeroHomHomologicalComplexPreadditiveHasZeroMorphismsToQuiverToCategoryStructInstCategoryHomologicalComplex = { zero := HomologicalComplex.Hom.mk fun (i : ι) => 0 }
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@[simp]
theorem HomologicalComplex.add_f_apply {ι : Type u_1} {V : Type u} [CategoryTheory.Category.{v, u} V] [CategoryTheory.Preadditive V] {c : ComplexShape ι} {C : HomologicalComplex V c} {D : HomologicalComplex V c} (f : C D) (g : C D) (i : ι) :
(f + g).f i = f.f i + g.f i
@[simp]
theorem HomologicalComplex.neg_f_apply {ι : Type u_1} {V : Type u} [CategoryTheory.Category.{v, u} V] [CategoryTheory.Preadditive V] {c : ComplexShape ι} {C : HomologicalComplex V c} {D : HomologicalComplex V c} (f : C D) (i : ι) :
(-f).f i = -f.f i
@[simp]
theorem HomologicalComplex.sub_f_apply {ι : Type u_1} {V : Type u} [CategoryTheory.Category.{v, u} V] [CategoryTheory.Preadditive V] {c : ComplexShape ι} {C : HomologicalComplex V c} {D : HomologicalComplex V c} (f : C D) (g : C D) (i : ι) :
(f - g).f i = f.f i - g.f i
@[simp]
theorem HomologicalComplex.nsmul_f_apply {ι : Type u_1} {V : Type u} [CategoryTheory.Category.{v, u} V] [CategoryTheory.Preadditive V] {c : ComplexShape ι} {C : HomologicalComplex V c} {D : HomologicalComplex V c} (n : ) (f : C D) (i : ι) :
(n f).f i = n f.f i
@[simp]
theorem HomologicalComplex.zsmul_f_apply {ι : Type u_1} {V : Type u} [CategoryTheory.Category.{v, u} V] [CategoryTheory.Preadditive V] {c : ComplexShape ι} {C : HomologicalComplex V c} {D : HomologicalComplex V c} (n : ) (f : C D) (i : ι) :
(n f).f i = n f.f i
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  • HomologicalComplex.instPreadditiveHomologicalComplexPreadditiveHasZeroMorphismsInstCategoryHomologicalComplex = CategoryTheory.Preadditive.mk
def HomologicalComplex.Hom.fAddMonoidHom {ι : Type u_1} {V : Type u} [CategoryTheory.Category.{v, u} V] [CategoryTheory.Preadditive V] {c : ComplexShape ι} {C₁ : HomologicalComplex V c} {C₂ : HomologicalComplex V c} (i : ι) :
(C₁ C₂) →+ (C₁.X i C₂.X i)

The i-th component of a chain map, as an additive map from chain maps to morphisms.

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    An additive functor induces a functor between homological complexes. This is sometimes called the "prolongation".

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      The functor on homological complexes induced by the identity functor is isomorphic to the identity functor.

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        An equivalence of categories induces an equivalences between the respective categories of homological complex.

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          theorem ChainComplex.map_chain_complex_of {V : Type u} [CategoryTheory.Category.{v, u} V] [CategoryTheory.Preadditive V] {W : Type u_2} [CategoryTheory.Category.{u_4, u_2} W] [CategoryTheory.Preadditive W] {α : Type u_3} [AddRightCancelSemigroup α] [One α] [DecidableEq α] (F : CategoryTheory.Functor V W) [CategoryTheory.Functor.Additive F] (X : αV) (d : (n : α) → X (n + 1) X n) (sq : ∀ (n : α), CategoryTheory.CategoryStruct.comp (d (n + 1)) (d n) = 0) :
          (CategoryTheory.Functor.mapHomologicalComplex F (ComplexShape.down α)).toPrefunctor.obj (ChainComplex.of X d sq) = ChainComplex.of (fun (n : α) => F.toPrefunctor.obj (X n)) (fun (n : α) => F.toPrefunctor.map (d n)) (_ : ∀ (n : α), CategoryTheory.CategoryStruct.comp ((fun (n : α) => F.toPrefunctor.map (d n)) (n + 1)) ((fun (n : α) => F.toPrefunctor.map (d n)) n) = 0)

          Turning an object into a complex supported at j then applying a functor is the same as applying the functor then forming the complex.

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