The homology of a complex #
Given C : HomologicalComplex V c
, we have C.cycles' i
and C.boundaries i
,
both defined as subobjects of C.X i
.
We show these are functorial with respect to chain maps,
as cyclesMap' f i
and boundariesMap f i
.
As a consequence we construct homologyFunctor' i : HomologicalComplex V c ⥤ V
,
computing the i
-th homology.
Note: Some definitions (specifically, names containing components homology
, cycles
)
in this file have the suffix '
so as to allow the development of the
new homology API of homological complex (starting from
Algebra.Homology.ShortComplex.HomologicalComplex
). It is planned that these definitions
shall be removed and replaced by the new API.
The cycles at index i
, as a subobject.
Equations
Instances For
The underlying object of C.cycles' i
is isomorphic to kernel (C.d i j)
,
for any j
such that Rel i j
.
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- One or more equations did not get rendered due to their size.
Instances For
The boundaries at index i
, as a subobject.
Equations
Instances For
The underlying object of C.boundaries j
is isomorphic to image (C.d i j)
,
for any i
such that Rel i j
.
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- One or more equations did not get rendered due to their size.
Instances For
The canonical map from boundaries i
to cycles' i
.
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Instances For
Prefer boundariesToCycles'
.
The homology of a complex at index i
.
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The j
th homology of a homological complex (as kernel of 'the differential from Cⱼ
' modulo
the image of 'the differential to Cⱼ
') is isomorphic to the kernel of d : Cⱼ → Cₖ
modulo
the image of d : Cᵢ → Cⱼ
when Rel i j
and Rel j k
.
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Instances For
The 0th homology of a chain complex is isomorphic to the cokernel of d : C₁ ⟶ C₀
.
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The 0th cohomology of a cochain complex is isomorphic to the kernel of d : C₀ → C₁
.
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- One or more equations did not get rendered due to their size.
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The n + 1
th homology of a chain complex (as kernel of 'the differential from Cₙ₊₁
' modulo
the image of 'the differential to Cₙ₊₁
') is isomorphic to the kernel of d : Cₙ₊₁ → Cₙ
modulo
the image of d : Cₙ₊₂ → Cₙ₊₁
.
Equations
Instances For
The n + 1
th cohomology of a cochain complex (as kernel of 'the differential from Cₙ₊₁
'
modulo the image of 'the differential to Cₙ₊₁
') is isomorphic to the kernel of d : Cₙ₊₁ → Cₙ₊₂
modulo the image of d : Cₙ → Cₙ₊₁
.
Equations
Instances For
Computing the cycles is functorial.
The morphism between cycles induced by a chain map.
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Cycles as a functor.
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Instances For
Computing the boundaries is functorial.
The morphism between boundaries induced by a chain map.
Equations
Instances For
Boundaries as a functor.
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The boundariesToCycles
morphisms are natural.
The natural transformation from the boundaries functor to the cycles functor.
Equations
- boundariesToCycles'NatTrans V c i = CategoryTheory.NatTrans.mk fun (C : HomologicalComplex V c) => HomologicalComplex.boundariesToCycles' C i
Instances For
The i
-th homology, as a functor to V
.
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Instances For
The homology functor from ι
-indexed complexes to ι
-graded objects in V
.
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