Predicate for localized categories #
In this file, a predicate L.IsLocalization W is introduced for a functor L : C ⥤ D
and W : MorphismProperty C: it expresses that L identifies D with the localized
category of C with respect to W (up to equivalence).
We introduce a universal property StrictUniversalPropertyFixedTarget L W E which
states that L inverts the morphisms in W and that all functors C ⥤ E inverting
W uniquely factor as a composition of L ⋙ G with G : D ⥤ E. Such universal
properties are inputs for the constructor IsLocalization.mk' for L.IsLocalization W.
When L : C ⥤ D is a localization functor for W : MorphismProperty (i.e. when
[L.IsLocalization W] holds), for any category E, there is
an equivalence FunctorEquivalence L W E : (D ⥤ E) ≌ (W.FunctorsInverting E)
that is induced by the composition with the functor L. When two functors
F : C ⥤ E and F' : D ⥤ E correspond via this equivalence, we shall say
that F' lifts F, and the associated isomorphism L ⋙ F' ≅ F is the
datum that is part of the class Lifting L W F F'. The functions
liftNatTrans and liftNatIso can be used to lift natural transformations
and natural isomorphisms between functors.
The predicate expressing that, up to equivalence, a functor L : C ⥤ D
identifies the category D with the localized category of C with respect
to W : MorphismProperty C.
- inverts : W.IsInvertedBy L
the functor inverts the given
MorphismProperty - isEquivalence : (Localization.Construction.lift L ⋯).IsEquivalence
the induced functor from the constructed localized category is an equivalence
Instances
This universal property states that a functor L : C ⥤ D inverts morphisms
in W and that all functors D ⥤ E (for a fixed category E) uniquely factor
through L.
- inverts : W.IsInvertedBy L
the functor
LinvertsW - lift (F : Functor C E) : W.IsInvertedBy F → Functor D E
any functor
C ⥤ Ewhich invertsWcan be lifted as a functorD ⥤ E there is a factorisation involving the lifted functor
uniqueness of the lifted functor
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The localized category W.Localization that was constructed satisfies
the universal property of the localization.
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When W consists of isomorphisms, the identity satisfies the universal property
of the localization.
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The isomorphism L.obj X ≅ L.obj Y that is deduced from a morphism f : X ⟶ Y which
belongs to W, when L.IsLocalization W.
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A chosen equivalence of categories W.Localization ≅ D for a functor
L : C ⥤ D which satisfies L.IsLocalization W. This shall be used in
order to deduce properties of L from properties of W.Q.
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Via the equivalence of categories equivalenceFromModel L W : W.Localization ≌ D,
one may identify the functors W.Q and L.
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Via the equivalence of categories equivalenceFromModel L W : W.Localization ≌ D,
one may identify the functors L and W.Q.
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The functor (D ⥤ E) ⥤ W.functors_inverting E induced by the composition
with a localization functor L : C ⥤ D with respect to W : MorphismProperty C.
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The equivalence of categories (D ⥤ E) ≌ (W.FunctorsInverting E) induced by
the composition with a localization functor L : C ⥤ D with respect to
W : MorphismProperty C.
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The functor (D ⥤ E) ⥤ (C ⥤ E) given by the composition with a localization
functor L : C ⥤ D with respect to W : MorphismProperty C.
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The precomposition with a localization functor gives fully faithful functors between functor categories.
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When L : C ⥤ D is a localization functor for W : MorphismProperty C and
F : C ⥤ E is a functor, we shall say that F' : D ⥤ E lifts F if the obvious diagram
is commutative up to an isomorphism.
the isomorphism relating the localization functor and the two other given functors
Instances
Given a localization functor L : C ⥤ D for W : MorphismProperty C and
a functor F : C ⥤ E which inverts W, this is a choice of functor
D ⥤ E which lifts F.
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The canonical isomorphism L ⋙ lift F hF L ≅ F for any functor F : C ⥤ E
which inverts W, when L : C ⥤ D is a localization functor for W.
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Given a localization functor L : C ⥤ D for W : MorphismProperty C,
if (F₁' F₂' : D ⥤ E) are functors which lift functors (F₁ F₂ : C ⥤ E),
a natural transformation τ : F₁ ⟶ F₂ uniquely lifts to a natural transformation F₁' ⟶ F₂'.
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Given a localization functor L : C ⥤ D for W : MorphismProperty C,
if (F₁' F₂' : D ⥤ E) are functors which lift functors (F₁ F₂ : C ⥤ E),
a natural isomorphism τ : F₁ ⟶ F₂ lifts to a natural isomorphism F₁' ⟶ F₂'.
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Given a localization functor L : C ⥤ D for W : MorphismProperty C,
if F₁' : D ⥤ E lifts a functor F₁ : C ⥤ D, then a functor F₂' which
is isomorphic to F₁' also lifts a functor F₂ that is isomorphic to F₁.
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If L : C ⥤ D is a localization for W : MorphismProperty C, then it is also
the case of a functor obtained by post-composing L with an equivalence of categories.
If L₁ : C ⥤ D₁ and L₂ : C ⥤ D₂ are two localization functors for the
same MorphismProperty C, this is an equivalence of categories D₁ ≌ D₂.
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The functor of equivalence of localized categories given by Localization.uniq is
compatible with the localization functors.
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The inverse functor of equivalence of localized categories given by Localization.uniq is
compatible with the localization functors.
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If L₁ : C ⥤ D₁ and L₂ : C ⥤ D₂ are two localization functors for the
same MorphismProperty C, any functor F : D₁ ⥤ D₂ equipped with an isomorphism
L₁ ⋙ F ≅ L₂ is isomorphic to the functor of the equivalence given by uniq.
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Localization of a category with respect to all morphisms results in a groupoid.
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The property that two morphisms become equal in the localized category.