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 C.cyclesMap f i
and C.boundariesMap f i
.
As a consequence we construct homologyFunctor i : HomologicalComplex V c ⥤ V
,
computing the i
-th homology.
The cycles at index i
, as a subobject.
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
.
Instances For
The boundaries at index i
, as a subobject.
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
.
Instances For
The canonical map from boundaries i
to cycles i
.
Instances For
Prefer boundariesToCycles
.
The homology of a complex at index i
.
Instances For
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
.
Instances For
The 0th homology of a chain complex is isomorphic to the cokernel of d : C₁ ⟶ C₀
.
Instances For
The 0th cohomology of a cochain complex is isomorphic to the kernel of d : C₀ → C₁
.
Instances For
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
.
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
.
Instances For
Computing the cycles is functorial.
The morphism between cycles induced by a chain map.
Instances For
Cycles as a functor.
Instances For
Computing the boundaries is functorial.
The morphism between boundaries induced by a chain map.
Instances For
Boundaries as a functor.
Instances For
The boundariesToCycles
morphisms are natural.
The natural transformation from the boundaries functor to the cycles functor.
Instances For
The i
-th homology, as a functor to V
.
Instances For
The homology functor from ι
-indexed complexes to ι
-graded objects in V
.