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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      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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        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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              instance quasiIso_comp {ι : Type u_2} {C : Type u} [CategoryTheory.Category.{v, u} C] [CategoryTheory.Limits.HasZeroMorphisms C] {c : ComplexShape ι} {K : HomologicalComplex C c} {L : HomologicalComplex C c} {M : HomologicalComplex C c} (φ : K L) (φ' : L M) [∀ (i : ι), HomologicalComplex.HasHomology K i] [∀ (i : ι), HomologicalComplex.HasHomology L i] [∀ (i : ι), HomologicalComplex.HasHomology M i] [hφ : QuasiIso φ] [hφ' : QuasiIso φ'] :
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