Tools for compatibilities between Dold-Kan equivalences
The purpose of this file is to introduce tools which will enable the
construction of the Dold-Kan equivalence SimplicialObject C ≌ ChainComplex C ℕ
for a pseudoabelian category C
from the equivalence
Karoubi (SimplicialObject C) ≌ Karoubi (ChainComplex C ℕ)
and the two
equivalences simplicial_object C ≅ Karoubi (SimplicialObject C)
and
ChainComplex C ℕ ≅ Karoubi (ChainComplex C ℕ)
.
It is certainly possible to get an equivalence SimplicialObject C ≌ ChainComplex C ℕ
using a compositions of the three equivalences above, but then neither the functor
nor the inverse would have good definitional properties. For example, it would be better
if the inverse functor of the equivalence was exactly the functor
Γ₀ : SimplicialObject C ⥤ ChainComplex C ℕ
which was constructed in FunctorGamma.lean
.
In this file, given four categories A
, A'
, B
, B'
, equivalences eA : A ≅ A'
,
eB : B ≅ B'
, e' : A' ≅ B'
, functors F : A ⥤ B'
, G : B ⥤ A
equipped with certain
compatibilities, we construct successive equivalences:
equivalence₀
fromA
toB'
, which is the composition ofeA
ande'
.equivalence₁
fromA
toB'
, with the same inverse functor asequivalence₀
, but whose functor isF
.equivalence₂
fromA
toB
, which is the composition ofequivalence₁
and the inverse ofeB
:equivalence
fromA
toB
, which has the same functorF ⋙ eB.inverse
asequivalence₂
, but whose inverse functor isG
.
When extra assumptions are given, we shall also provide simplification lemmas for the
unit and counit isomorphisms of equivalence
.
(See Equivalence.lean
for the general strategy of proof of the Dold-Kan equivalence.)
A basic equivalence A ≅ B'
obtained by composing eA : A ≅ A'
and e' : A' ≅ B'
.
Equations
- AlgebraicTopology.DoldKan.Compatibility.equivalence₀ eA e' = eA.trans e'
Instances For
An intermediate equivalence A ≅ B'
whose functor is F
and whose inverse is
e'.inverse ⋙ eA.inverse
.
Equations
- AlgebraicTopology.DoldKan.Compatibility.equivalence₁ hF = (AlgebraicTopology.DoldKan.Compatibility.equivalence₀ eA e').changeFunctor hF
Instances For
The counit isomorphism of the equivalence equivalence₁
between A
and B'
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The unit isomorphism of the equivalence equivalence₁
between A
and B'
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
An intermediate equivalence A ≅ B
obtained as the composition of equivalence₁
and
the inverse of eB : B ≌ B'
.
Equations
- AlgebraicTopology.DoldKan.Compatibility.equivalence₂ eB hF = (AlgebraicTopology.DoldKan.Compatibility.equivalence₁ hF).trans eB.symm
Instances For
The counit isomorphism of the equivalence equivalence₂
between A
and B
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The unit isomorphism of the equivalence equivalence₂
between A
and B
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The equivalence A ≅ B
whose functor is F ⋙ eB.inverse
and
whose inverse is G : B ≅ A
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The isomorphism eB.functor ⋙ e'.inverse ⋙ e'.functor ≅ eB.functor
deduced
from the counit isomorphism of e'
.
Equations
- AlgebraicTopology.DoldKan.Compatibility.τ₀ = Trans.trans (CategoryTheory.isoWhiskerLeft eB.functor e'.counitIso) eB.functor.rightUnitor
Instances For
The isomorphism eB.functor ⋙ e'.inverse ⋙ e'.functor ≅ eB.functor
deduced
from the isomorphisms hF : eA.functor ⋙ e'.functor ≅ F
,
hG : eB.functor ⋙ e'.inverse ≅ G ⋙ eA.functor
and the datum of
an isomorphism η : G ⋙ F ≅ eB.functor
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The counit isomorphism of equivalence
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The isomorphism eA.functor ≅ F ⋙ e'.inverse
deduced from the
unit isomorphism of e'
and the isomorphism hF : eA.functor ⋙ e'.functor ≅ F
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The unit isomorphism of equivalence
.
Equations
- One or more equations did not get rendered due to their size.