Behaviour of the total complex with respect to shifts #
There are two ways to shift objects in HomologicalComplex₂ C (up ℤ) (up ℤ)
:
- by shifting the first indices (and changing signs of horizontal differentials),
which corresponds to the shift by
ℤ
onCochainComplex (CochainComplex C ℤ) ℤ
. - by shifting the second indices (and changing signs of vertical differentials).
These two sorts of shift functors shall be abbreviated as
HomologicalComplex₂.shiftFunctor₁ C x
and
HomologicalComplex₂.shiftFunctor₂ C y
.
In this file, for any K : HomologicalComplex₂ C (up ℤ) (up ℤ)
, we define an isomorphism
K.totalShift₁Iso x : ((shiftFunctor₁ C x).obj K).total (up ℤ) ≅ (K.total (up ℤ))⟦x⟧
for any x : ℤ
(which does not involve signs) and an isomorphism
K.totalShift₂Iso y : ((shiftFunctor₂ C y).obj K).total (up ℤ) ≅ (K.total (up ℤ))⟦y⟧
for any y : ℤ
(which is given by the multiplication by (p * y).negOnePow
on the
summand in bidegree (p, q)
of K
).
Depending on the order of the "composition" of the two isomorphisms
totalShift₁Iso
and totalShift₂Iso
, we get
two ways to identify ((shiftFunctor₁ C x).obj ((shiftFunctor₂ C y).obj K)).total (up ℤ)
and (K.total (up ℤ))⟦x + y⟧
. The lemma totalShift₁Iso_trans_totalShift₂Iso
shows that
these two compositions of isomorphisms differ by the sign (x * y).negOnePow
.
The shift on bicomplexes obtained by shifting the first indices (and changing the sign of differentials).
Equations
Instances For
The shift on bicomplexes obtained by shifting the second indices (and changing the sign of differentials).
Equations
- HomologicalComplex₂.shiftFunctor₂ C y = (CategoryTheory.shiftFunctor (HomologicalComplex C (ComplexShape.up ℤ)) y).mapHomologicalComplex (ComplexShape.up ℤ)
Instances For
The isomorphism (((shiftFunctor₁ C x).obj K).X a).X b ≅ (K.X a').X b
when a' = a + x
.
Equations
- K.shiftFunctor₁XXIso a x a' h b = CategoryTheory.eqToIso ⋯
Instances For
The isomorphism (((shiftFunctor₂ C y).obj K).X a).X b ≅ (K.X a).X b'
when b' = b + y
.
Equations
- K.shiftFunctor₂XXIso a b y b' h = CategoryTheory.eqToIso ⋯
Instances For
Auxiliary definition for totalShift₁Iso
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The isomorphism ((shiftFunctor₁ C x).obj K).total (up ℤ) ≅ (K.total (up ℤ))⟦x⟧
expressing the compatibility of the total complex with the shift on the first indices.
This isomorphism does not involve signs.
Equations
- K.totalShift₁Iso x = HomologicalComplex.Hom.isoOfComponents (fun (n : ℤ) => K.totalShift₁XIso x n (n + x) ⋯) ⋯
Instances For
Auxiliary definition for totalShift₂Iso
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The isomorphism ((shiftFunctor₂ C y).obj K).total (up ℤ) ≅ (K.total (up ℤ))⟦y⟧
expressing the compatibility of the total complex with the shift on the second indices.
This isomorphism involves signs: on the summand in degree (p, q)
of K
, it is given by the
multiplication by (p * y).negOnePow
.
Equations
- K.totalShift₂Iso y = HomologicalComplex.Hom.isoOfComponents (fun (n : ℤ) => K.totalShift₂XIso y n (n + y) ⋯) ⋯
Instances For
The shift functors shiftFunctor₁ C x
and shiftFunctor₂ C y
on bicomplexes
with respect to both variables commute.
Equations
Instances For
The compatibility isomorphisms of the total complex with the shifts
in both variables "commute" only up to a sign (x * y).negOnePow
.
The compatibility isomorphisms of the total complex with the shifts
in both variables "commute" only up to a sign (x * y).negOnePow
.