Light profinite spaces #
We construct the category LightProfinite
of light profinite topological spaces. These are
implemented as totally disconnected second countable compact Hausdorff spaces.
This file also defines the category LightDiagram
, which consists of those spaces that can be
written as a sequential limit (in Profinite
) of finite sets.
We define an equivalence of categories LightProfinite ≌ LightDiagram
and prove that these are
essentially small categories.
LightProfinite
is the category of second countable profinite spaces.
- toCompHaus : CompHaus
The underlying compact Hausdorff space of a light profinite space.
- isTotallyDisconnected : TotallyDisconnectedSpace ↑self.toCompHaus.toTop
A light profinite space is totally disconnected
- secondCountable : SecondCountableTopology ↑self.toCompHaus.toTop
A light profinite space is second countable
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A light profinite space is totally disconnected
A light profinite space is second countable
Construct a term of LightProfinite
from a type endowed with the structure of a compact,
Hausdorff, totally disconnected and second countable topological space.
Equations
- LightProfinite.of X = LightProfinite.mk (CompHausLike.mk { α := X, str := inferInstance } trivial)
Instances For
Equations
- LightProfinite.instInhabited = { default := LightProfinite.of PEmpty.{u_1 + 1} }
Equations
- LightProfinite.hasForget₂ = CategoryTheory.InducedCategory.hasForget₂ fun (X : CategoryTheory.InducedCategory CompHaus LightProfinite.toCompHaus) => X.toCompHaus.toTop
Equations
- LightProfinite.instCoeSortType = { coe := fun (X : LightProfinite) => ↑X.toCompHaus.toTop }
Equations
- ⋯ = ⋯
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- ⋯ = ⋯
Equations
- LightProfinite.instTopologicalSpaceObjForget = let_fun this := inferInstance; this
Equations
- ⋯ = ⋯
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- ⋯ = ⋯
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- ⋯ = ⋯
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- ⋯ = ⋯
The fully faithful embedding of LightProfinite
in Profinite
.
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lightToProfinite
is fully faithful.
Equations
- lightToProfiniteFullyFaithful = CategoryTheory.fullyFaithfulInducedFunctor fun (X : LightProfinite) => Profinite.of ↑X.toCompHaus.toTop
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The fully faithful embedding of LightProfinite
in CompHaus
.
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Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
The fully faithful embedding of LightProfinite
in TopCat
.
This is definitionally the same as the obvious composite.
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LightProfinite.toTopCat
is fully faithful.
Equations
- LightProfinite.toTopCatFullyFaithful = CategoryTheory.fullyFaithfulInducedFunctor fun (X : CategoryTheory.InducedCategory CompHaus LightProfinite.toCompHaus) => X.toCompHaus.toTop
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Equations
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The natural functor from Fintype
to LightProfinite
, endowing a finite type with the
discrete topology.
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FintypeCat.toLightProfinite
is fully faithful.
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Equations
- ⋯ = ⋯
An explicit limit cone for a functor F : J ⥤ LightProfinite
, for a countable category J
defined in terms of CompHaus.limitCone
, which is defined in terms of TopCat.limitCone
.
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The limit cone LightProfinite.limitCone F
is indeed a limit cone.
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Any morphism of light profinite spaces is a closed map.
Any continuous bijection of light profinite spaces induces an isomorphism.
Any continuous bijection of light profinite spaces induces an isomorphism.
Equations
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Construct an isomorphism from a homeomorphism.
Equations
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Construct a homeomorphism from an isomorphism.
Equations
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The equivalence between isomorphisms in LightProfinite
and homeomorphisms
of topological spaces.
Equations
- LightProfinite.isoEquivHomeo = { toFun := LightProfinite.homeoOfIso, invFun := LightProfinite.isoOfHomeo, left_inv := ⋯, right_inv := ⋯ }
Instances For
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
A structure containing the data of sequential limit in Profinite
of finite sets.
- diagram : CategoryTheory.Functor ℕᵒᵖ FintypeCat
The indexing diagram.
- cone : CategoryTheory.Limits.Cone (self.diagram.comp FintypeCat.toProfinite)
The limit cone.
- isLimit : CategoryTheory.Limits.IsLimit self.cone
The limit cone is limiting.
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The fully faithful embedding LightDiagram ⥤ Profinite
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Equations
- instTopologicalSpaceObjLightDiagramForget = inferInstance
Equations
- ⋯ = ⋯
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- ⋯ = ⋯
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- ⋯ = ⋯
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- ⋯ = ⋯
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- ⋯ = ⋯
A profinite space which is light gives rise to a light profinite space.
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The functor part of the equivalence LightProfinite ≌ LightDiagram
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- One or more equations did not get rendered due to their size.
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Equations
- ⋯ = ⋯
The inverse part of the equivalence LightProfinite ≌ LightDiagram
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- One or more equations did not get rendered due to their size.
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The equivalence of categories LightProfinite ≌ LightDiagram
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This is an auxiliary definition used to show that LightDiagram
is essentially small.
Note that below we put a category instance on this structure which is completely different from the
category instance on ℕᵒᵖ ⥤ FintypeCat.Skeleton.{u}
. Neither the morphisms nor the objects are the
same.
- diagram : CategoryTheory.Functor ℕᵒᵖ FintypeCat.Skeleton
The diagram takes values in a small category equivalent to
FintypeCat
.
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A LightDiagram'
yields a Profinite
.
Equations
- S.toProfinite = CategoryTheory.Limits.limit (S.diagram.comp (FintypeCat.Skeleton.equivalence.functor.comp FintypeCat.toProfinite))
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The functor part of the equivalence of categories LightDiagram' ≌ LightDiagram
.
Equations
- One or more equations did not get rendered due to their size.
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The equivalence beween LightDiagram
and a small category.
Equations
- LightDiagram.equivSmall = LightDiagram'.toLightFunctor.asEquivalence.symm