The canonical truncation #
Given an embedding e : Embedding c c'
of complex shapes which
satisfies e.IsTruncGE
and K : HomologicalComplex C c'
,
we define K.truncGE' e : HomologicalComplex C c
and K.truncGE e : HomologicalComplex C c'
which are the canonical
truncations of K
relative to e
.
For example, if e
is the embedding embeddingUpIntGE p
of ComplexShape.up ℕ
in ComplexShape.up ℤ
which sends n : ℕ
to p + n
and K : CochainComplex C ℤ
,
then K.truncGE' e : CochainComplex C ℕ
is the following complex:
Q ⟶ K.X (p + 1) ⟶ K.X (p + 2) ⟶ K.X (p + 3) ⟶ ...
where in degree 0
, the object Q
identifies to the cokernel
of K.X (p - 1) ⟶ K.X p
(this is K.opcycles p
). Then, the
cochain complex K.truncGE e
is indexed by ℤ
, and has the
following shape:
... ⟶ 0 ⟶ 0 ⟶ 0 ⟶ Q ⟶ K.X (p + 1) ⟶ K.X (p + 2) ⟶ K.X (p + 3) ⟶ ...
where Q
is in degree p
.
TODO #
- construct a morphism
K.πTruncGE e : K ⟶ K.truncGE e
and show that it induces an isomorphism in homology in degrees in the image ofe.f
.
Equations
- HomologicalComplex.truncGE'.X K e i = if e.BoundaryGE i then K.opcycles (e.f i) else K.X (e.f i)
Instances For
The isomorphism truncGE'.X K e i ≅ K.opcycles (e.f i)
when e.BoundaryGE i
holds.
Equations
Instances For
The isomorphism truncGE'.X K e i ≅ K.X (e.f i)
when e.BoundaryGE i
does not hold.
Equations
Instances For
Equations
- One or more equations did not get rendered due to their size.
Instances For
The canonical truncation of a homological complex relative to an embedding
of complex shapes e
which satisfies e.IsTruncGE
.
Equations
- K.truncGE' e = { X := HomologicalComplex.truncGE'.X K e, d := HomologicalComplex.truncGE'.d K e, shape := ⋯, d_comp_d' := ⋯ }
Instances For
The isomorphism (K.truncGE' e).X i ≅ K.X i'
when e.f i = i'
and e.BoundaryGE i
does not hold.
Equations
- K.truncGE'XIso e hi' hi = HomologicalComplex.truncGE'.XIso K e hi ≪≫ CategoryTheory.eqToIso ⋯
Instances For
The isomorphism (K.truncGE' e).X i ≅ K.opcycles i'
when e.f i = i'
and e.BoundaryGE i
holds.
Equations
- K.truncGE'XIsoOpcycles e hi' hi = HomologicalComplex.truncGE'.XIsoOpcycles K e hi ≪≫ CategoryTheory.eqToIso ⋯
Instances For
The canonical truncation of a homological complex relative to an embedding
of complex shapes e
which satisfies e.IsTruncGE
.
Equations
- K.truncGE e = (K.truncGE' e).extend e
Instances For
The isomorphism (K.truncGE e).X i' ≅ K.X i'
when e.f i = i'
and e.BoundaryGE i
does not hold.
Instances For
The isomorphism (K.truncGE e).X i' ≅ K.opcycles i'
when e.f i = i'
and e.BoundaryGE i
holds.
Equations
Instances For
The morphism K.truncGE' e ⟶ L.truncGE' e
induced by a morphism K ⟶ L
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The morphism K.truncGE e ⟶ L.truncGE e
induced by a morphism K ⟶ L
.
Equations
- HomologicalComplex.truncGEMap φ e = (e.extendFunctor C).map (HomologicalComplex.truncGE'Map φ e)
Instances For
Given an embedding e : Embedding c c'
of complex shapes which satisfy e.IsTruncGE
,
this is the (canonical) truncation functor
HomologicalComplex C c' ⥤ HomologicalComplex C c
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Given an embedding e : Embedding c c'
of complex shapes which satisfy e.IsTruncGE
,
this is the (canonical) truncation functor
HomologicalComplex C c' ⥤ HomologicalComplex C c'
.
Equations
- One or more equations did not get rendered due to their size.