The short complexes attached to homological complexes #
In this file, we define a functor
shortComplexFunctor C c i : HomologicalComplex C c ⥤ ShortComplex C.
By definition, the image of a homological complex K by this functor
is the short complex K.X (c.prev i) ⟶ K.X i ⟶ K.X (c.next i).
The homology K.homology i of a homological complex K in degree i is defined as
the homology of the short complex (shortComplexFunctor C c i).obj K, which can be
abbreviated as K.sc i.
The functor HomologicalComplex C c ⥤ ShortComplex C which sends a homological
complex K to the short complex K.X i ⟶ K.X j ⟶ K.X k for arbitrary indices i, j and k.
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The functor HomologicalComplex C c ⥤ ShortComplex C which sends a homological
complex K to the short complex K.X (c.prev i) ⟶ K.X i ⟶ K.X (c.next i).
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- HomologicalComplex.shortComplexFunctor C c i = HomologicalComplex.shortComplexFunctor' C c (ComplexShape.prev c i) i (ComplexShape.next c i)
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The natural isomorphism shortComplexFunctor C c j ≅ shortComplexFunctor' C c i j k
when c.prev j = i and c.next j = k.
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The short complex K.X i ⟶ K.X j ⟶ K.X k for arbitrary indices i, j and k.
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- HomologicalComplex.sc' K i j k = (HomologicalComplex.shortComplexFunctor' C c i j k).obj K
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The short complex K.X (c.prev i) ⟶ K.X i ⟶ K.X (c.next i).
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- HomologicalComplex.sc K i = (HomologicalComplex.shortComplexFunctor C c i).obj K
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The canonical isomorphism K.sc j ≅ K.sc' i j k when c.prev j = i and c.next j = k.
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- HomologicalComplex.isoSc' K i j k hi hk = (HomologicalComplex.natIsoSc' C c i j k hi hk).app K
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A homological complex K has homology in degree i if the associated
short complex K.sc i has.
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The homology in degree i of a homological complex.
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Comparison isomorphism between the homology for the two homology API.
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The cycles in degree i of a homological complex.
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The inclusion of the cycles of a homological complex.
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The homology class map from cycles to the homology of a homological complex.
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The morphism to K.cycles i that is induced by a "cycle", i.e. a morphism
to K.X i whose postcomposition with the differential is zero.
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- HomologicalComplex.liftCycles K k j hj hk = CategoryTheory.ShortComplex.liftCycles (HomologicalComplex.sc K i) k ⋯
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The morphism to K.cycles i that is induced by a "cycle", i.e. a morphism
to K.X i whose postcomposition with the differential is zero.
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- HomologicalComplex.liftCycles' K k j hj hk = HomologicalComplex.liftCycles K k j ⋯ hk
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The map K.X i ⟶ K.cycles j induced by the differential K.d i j.
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- HomologicalComplex.toCycles K i j = HomologicalComplex.liftCycles K (K.d i j) (ComplexShape.next c j) ⋯ ⋯
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K.cycles i is the kernel of K.d i j when c.next i = j.
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- ⋯ = ⋯
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- ⋯ = ⋯
K.homology j is the cokernel of K.toCycles i j : K.X i ⟶ K.cycles j
when c.prev j = i.
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The opcycles in degree i of a homological complex.
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The projection to the opcycles of a homological complex.
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The inclusion map of the homology of a homological complex into its opcycles.
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The morphism from K.opcycles i that is induced by an "opcycle", i.e. a morphism
from K.X i whose precomposition with the differential is zero.
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- HomologicalComplex.descOpcycles K k j hj hk = CategoryTheory.ShortComplex.descOpcycles (HomologicalComplex.sc K i) k ⋯
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The morphism from K.opcycles i that is induced by an "opcycle", i.e. a morphism
from K.X i whose precomposition with the differential is zero.
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- HomologicalComplex.descOpcycles' K k j hj hk = HomologicalComplex.descOpcycles K k j ⋯ hk
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The map K.opcycles i ⟶ K.X j induced by the differential K.d i j.
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- HomologicalComplex.fromOpcycles K i j = HomologicalComplex.descOpcycles K (K.d i j) (ComplexShape.prev c i) ⋯ ⋯
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K.opcycles j is the cokernel of K.d i j when c.prev j = i.
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- ⋯ = ⋯
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- ⋯ = ⋯
K.homology i is the kernel of K.fromOpcycles i j : K.opcycles i ⟶ K.X j
when c.next i = j.
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The map K.homology i ⟶ L.homology i induced by a morphism in HomologicalComplex.
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The map K.cycles i ⟶ L.cycles i induced by a morphism in HomologicalComplex.
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The map K.opcycles i ⟶ L.opcycles i induced by a morphism in HomologicalComplex.
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- ⋯ = ⋯
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- ⋯ = ⋯
The ith homology functor HomologicalComplex C c ⥤ C.
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The homology functor to graded objects.
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The ith cycles functor HomologicalComplex C c ⥤ C.
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The ith opcycles functor HomologicalComplex C c ⥤ C.
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The natural transformation K.homologyπ i : K.cycles i ⟶ K.homology i
for all K : HomologicalComplex C c.
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- HomologicalComplex.natTransHomologyπ C c i = { app := fun (K : HomologicalComplex C c) => HomologicalComplex.homologyπ K i, naturality := ⋯ }
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The natural transformation K.homologyι i : K.homology i ⟶ K.opcycles i
for all K : HomologicalComplex C c.
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- HomologicalComplex.natTransHomologyι C c i = { app := fun (K : HomologicalComplex C c) => HomologicalComplex.homologyι K i, naturality := ⋯ }
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The natural isomorphism K.homology i ≅ (K.sc i).homology
for all homological complexes K.
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The natural isomorphism K.homology j ≅ (K.sc' i j k).homology
for all homological complexes K when c.prev j = i and c.next j = k.
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- ⋯ = ⋯
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- ⋯ = ⋯
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- ⋯ = ⋯
The canonical isomorphism K.cycles i ≅ K.X i when the differential from i is zero.
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- HomologicalComplex.iCyclesIso K i j hj h = let_fun this := ⋯; CategoryTheory.asIso (HomologicalComplex.iCycles K i)
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The canonical isomorphism K.homology i ≅ K.opcycles i
when the differential from i is zero.
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- HomologicalComplex.isoHomologyι K i j hj h = let_fun this := ⋯; CategoryTheory.asIso (HomologicalComplex.homologyι K i)
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The canonical isomorphism K.X j ≅ K.opCycles j when the differential to j is zero.
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- HomologicalComplex.pOpcyclesIso K i j hi h = let_fun this := ⋯; CategoryTheory.asIso (HomologicalComplex.pOpcycles K j)
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The canonical isomorphism K.cycles j ≅ K.homology j
when the differential to j is zero.
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- HomologicalComplex.isoHomologyπ K i j hi h = let_fun this := ⋯; CategoryTheory.asIso (HomologicalComplex.homologyπ K j)
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A homological complex K is exact at i if the short complex K.sc i is exact.
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- ⋯ = ⋯
The canonical isomorphism K.homology 0 ≅ K.opcycles 0 for a chain complex K
indexed by ℕ.
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- ⋯ = ⋯
The canonical isomorphism K.cycles 0 ≅ K.homology 0 for a cochain complex K
indexed by ℕ.
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- ⋯ = ⋯
The cycles of a homological complex in degree j can be computed
by specifying a choice of c.prev j and c.next j.
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- HomologicalComplex.cyclesIsoSc' K i j k hi hk = CategoryTheory.ShortComplex.cyclesMapIso (HomologicalComplex.isoSc' K i j k hi hk)
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The homology of a homological complex in degree j can be computed
by specifying a choice of c.prev j and c.next j.
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- HomologicalComplex.opcyclesIsoSc' K i j k hi hk = CategoryTheory.ShortComplex.opcyclesMapIso (HomologicalComplex.isoSc' K i j k hi hk)
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The opcycles of a homological complex in degree j can be computed
by specifying a choice of c.prev j and c.next j.
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- HomologicalComplex.homologyIsoSc' K i j k hi hk = CategoryTheory.ShortComplex.homologyMapIso (HomologicalComplex.isoSc' K i j k hi hk)