Documentation

Mathlib.Algebra.Homology.QuasiIso

Quasi-isomorphisms #

A chain map is a quasi-isomorphism if it induces isomorphisms on homology.

Future work #

Define the derived category as the localization at quasi-isomorphisms? (TODO @joelriou)

A chain map is a quasi-isomorphism if it induces isomorphisms on homology.

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    If a chain map f : X ⟶ Y[0] is a quasi-isomorphism, then the cokernel of the differential d : X₁ → X₀ is isomorphic to Y.

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      theorem HomologicalComplex.Hom.to_single₀_exact_at_succ {W : Type u_2} [CategoryTheory.Category.{u_3, u_2} W] [CategoryTheory.Abelian W] {X : ChainComplex W } {Y : W} (f : X (ChainComplex.single₀ W).toPrefunctor.obj Y) [hf : QuasiIso' f] (n : ) :
      CategoryTheory.Exact (X.d (n + 2) (n + 1)) (X.d (n + 1) n)

      If a cochain map f : Y[0] ⟶ X is a quasi-isomorphism, then the kernel of the differential d : X₀ → X₁ is isomorphic to Y.

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        theorem HomologicalComplex.Hom.from_single₀_exact_at_succ {W : Type u_2} [CategoryTheory.Category.{u_3, u_2} W] [CategoryTheory.Abelian W] {X : CochainComplex W } {Y : W} (f : (CochainComplex.single₀ W).toPrefunctor.obj Y X) [hf : QuasiIso' f] (n : ) :
        CategoryTheory.Exact (X.d n (n + 1)) (X.d (n + 1) (n + 2))

        A morphism of homological complexes f : K ⟶ L is a quasi-isomorphism in degree i when it induces a quasi-isomorphism of short complexes K.sc i ⟶ L.sc i.

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          The isomorphism K.homology i ≅ L.homology i induced by a morphism f : K ⟶ L such that [QuasiIsoAt f i] holds.

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            A morphism of homological complexes f : K ⟶ L is a quasi-isomorphism when it is so in every degree, i.e. when the induced maps homologyMap f i : K.homology i ⟶ L.homology i are all isomorphisms (see quasiIso_iff and quasiIsoAt_iff_isIso_homologyMap).

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