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Mathlib.CategoryTheory.MorphismProperty.Limits

Relation of morphism properties with limits #

The following predicates are introduces for morphism properties P:

We define P.universally for the class of morphisms which satisfy P after any base change.

We also introduce properties IsStableUnderProductsOfShape, IsStableUnderLimitsOfShape, IsStableUnderFiniteProducts, and similar properties for colimits and coproducts.

Given a class of morphisms P, this is the class of pullbacks of morphisms in P.

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      theorem CategoryTheory.MorphismProperty.pullbacks_mk {C : Type u} [Category.{v, u} C] (P : MorphismProperty C) {A B X Y : C} {f : A ⟢ X} {q : A ⟢ B} {p : X ⟢ Y} {g : B ⟢ Y} (sq : IsPullback f q p g) (hp : P p) :

      Given a class of morphisms P, this is the class of pushouts of morphisms in P.

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          theorem CategoryTheory.MorphismProperty.pushouts_mk {C : Type u} [Category.{v, u} C] (P : MorphismProperty C) {A B X Y : C} {f : A ⟢ X} {q : A ⟢ B} {p : X ⟢ Y} {g : B ⟢ Y} (sq : IsPushout f q p g) (hq : P q) :
          theorem CategoryTheory.MorphismProperty.isomorphisms_le_pushouts {C : Type u} [Category.{v, u} C] (P : MorphismProperty C) (h : βˆ€ (X : C), βˆƒ (A : C) (B : C) (p : A ⟢ B) (_ : P p) (x : B ⟢ X), IsIso p) :

          If P : MorphismProperty C is such that any object in C maps to the target of some morphism in P, then P.pushouts contains the isomorphisms.

          A morphism property is IsStableUnderBaseChange if the base change of such a morphism still falls in the class.

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            A morphism property is IsStableUnderCobaseChange if the cobase change of such a morphism still falls in the class.

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              P.HasPullbacksAlong f states that for any morphism satisfying P with the same codomain as f, the pullback of that morphism along f exists.

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                P.IsStableUnderBaseChangeAlong f states that for any morphism satisfying P with the same codomain as f, any pullback of that morphism along f also satisfies P.

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                  theorem CategoryTheory.MorphismProperty.of_isPullback {C : Type u} [Category.{v, u} C] {P : MorphismProperty C} [P.IsStableUnderBaseChange] {X Y Y' S : C} {f : X ⟢ S} {g : Y ⟢ S} {f' : Y' ⟢ Y} {g' : Y' ⟢ X} (sq : IsPullback f' g' g f) (hg : P g) :
                  P g'
                  theorem CategoryTheory.MorphismProperty.IsStableUnderBaseChange.mk' {C : Type u} [Category.{v, u} C] {P : MorphismProperty C} [P.RespectsIso] (hPβ‚‚ : βˆ€ (X Y S : C) (f : X ⟢ S) (g : Y ⟢ S) [inst : Limits.HasPullback f g], P g β†’ P (Limits.pullback.fst f g)) :

                  Alternative constructor for IsStableUnderBaseChange.

                  theorem CategoryTheory.MorphismProperty.IsStableUnderBaseChange.of_forall_exists_isPullback {C : Type u} [Category.{v, u} C] {P : MorphismProperty C} [P.RespectsIso] (H : βˆ€ {X Y Z : C} (f : X ⟢ Z) (g : Y ⟢ Z) [Limits.HasPullback f g], P g β†’ βˆƒ (T : C) (fst : T ⟢ X) (snd : T ⟢ Y), IsPullback fst snd f g ∧ P fst) :
                  theorem CategoryTheory.MorphismProperty.baseChange_map' {C : Type u} [Category.{v, u} C] {P : MorphismProperty C} [P.IsStableUnderBaseChange] {S S' X Y : C} (f : S' ⟢ S) {v₁₂ : X ⟢ S} {vβ‚‚β‚‚ : Y ⟢ S} {g : X ⟢ Y} (hv₁₂ : v₁₂ = CategoryStruct.comp g vβ‚‚β‚‚) [Limits.HasPullback v₁₂ f] [Limits.HasPullback vβ‚‚β‚‚ f] (H : P g) :
                  P (Limits.pullback.lift (CategoryStruct.comp (Limits.pullback.fst v₁₂ f) g) (Limits.pullback.snd v₁₂ f) β‹―)
                  theorem CategoryTheory.MorphismProperty.pullback_map {C : Type u} [Category.{v, u} C] {P : MorphismProperty C} [P.IsStableUnderBaseChange] [P.IsStableUnderComposition] {S X X' Y Y' : C} {f : X ⟢ S} [Limits.HasPullbacksAlong f] {g : Y ⟢ S} {f' : X' ⟢ S} {g' : Y' ⟢ S} {i₁ : X ⟢ X'} [Limits.HasPullbacksAlong g'] {iβ‚‚ : Y ⟢ Y'} (h₁ : P i₁) (hβ‚‚ : P iβ‚‚) (e₁ : f = CategoryStruct.comp i₁ f') (eβ‚‚ : g = CategoryStruct.comp iβ‚‚ g') :
                  P (Limits.pullback.map f g f' g' i₁ iβ‚‚ (CategoryStruct.id S) β‹― β‹―)
                  theorem CategoryTheory.MorphismProperty.of_isPushout {C : Type u} [Category.{v, u} C] {P : MorphismProperty C} [P.IsStableUnderCobaseChange] {A A' B B' : C} {f : A ⟢ A'} {g : A ⟢ B} {f' : B ⟢ B'} {g' : A' ⟢ B'} (sq : IsPushout g f f' g') (hf : P f) :
                  P f'
                  theorem CategoryTheory.MorphismProperty.IsStableUnderCobaseChange.mk' {C : Type u} [Category.{v, u} C] {P : MorphismProperty C} [P.RespectsIso] (hPβ‚‚ : βˆ€ (A B A' : C) (f : A ⟢ A') (g : A ⟢ B) [inst : Limits.HasPushout f g], P f β†’ P (Limits.pushout.inr f g)) :

                  An alternative constructor for IsStableUnderCobaseChange.

                  theorem CategoryTheory.MorphismProperty.IsStableUnderCobaseChange.of_forall_exists_isPullback {C : Type u} [Category.{v, u} C] {P : MorphismProperty C} [P.RespectsIso] (H : βˆ€ {X Y Z : C} (f : Z ⟢ X) (g : Z ⟢ Y) [Limits.HasPushout f g], P f β†’ βˆƒ (T : C) (inl : X ⟢ T) (inr : Y ⟢ T), IsPushout f g inl inr ∧ P inr) :

                  The class of morphisms in C that are limits of shape J of natural transformations involving morphisms in W.

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                    theorem CategoryTheory.MorphismProperty.limitsOfShape.mk' {C : Type u} [Category.{v, u} C] {W : MorphismProperty C} {J : Type u_1} [Category.{v_1, u_1} J] (X₁ Xβ‚‚ : Functor J C) (c₁ : Limits.Cone X₁) (cβ‚‚ : Limits.Cone Xβ‚‚) (h₁ : Limits.IsLimit c₁) (hβ‚‚ : Limits.IsLimit cβ‚‚) (f : X₁ ⟢ Xβ‚‚) (hf : W.functorCategory J f) (Ο† : c₁.pt ⟢ cβ‚‚.pt) (hΟ† : βˆ€ (j : J), CategoryStruct.comp Ο† (cβ‚‚.Ο€.app j) = CategoryStruct.comp (c₁.Ο€.app j) (f.app j)) :
                    W.limitsOfShape J Ο†

                    The property that a morphism property W is stable under limits indexed by a category J.

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                      The class of morphisms in C that are colimits of shape J of natural transformations involving morphisms in W.

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                        theorem CategoryTheory.MorphismProperty.colimitsOfShape.mk' {C : Type u} [Category.{v, u} C] {W : MorphismProperty C} {J : Type u_1} [Category.{v_1, u_1} J] (X₁ Xβ‚‚ : Functor J C) (c₁ : Limits.Cocone X₁) (cβ‚‚ : Limits.Cocone Xβ‚‚) (h₁ : Limits.IsColimit c₁) (hβ‚‚ : Limits.IsColimit cβ‚‚) (f : X₁ ⟢ Xβ‚‚) (hf : W.functorCategory J f) (Ο† : c₁.pt ⟢ cβ‚‚.pt) (hΟ† : βˆ€ (j : J), CategoryStruct.comp (c₁.ΞΉ.app j) Ο† = CategoryStruct.comp (f.app j) (cβ‚‚.ΞΉ.app j)) :

                        The property that a morphism property W is stable under colimits indexed by a category J.

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                          The condition that a property of morphisms is stable by filtered colimits.

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                            Given W : MorphismProperty C, this is class of morphisms that are isomorphic to a coproduct of a family (indexed by some J : Type w) of maps in W.

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                                @[reducible, inline]

                                The property that a morphism property W is stable under products indexed by a type J.

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                                    @[reducible, inline]

                                    The property that a morphism property W is stable under coproducts indexed by a type J.

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                                        theorem CategoryTheory.MorphismProperty.IsStableUnderProductsOfShape.mk {C : Type u} [Category.{v, u} C] (W : MorphismProperty C) (J : Type u_1) [W.RespectsIso] (hW : βˆ€ (X₁ Xβ‚‚ : J β†’ C) [inst : Limits.HasProduct X₁] [inst_1 : Limits.HasProduct Xβ‚‚] (f : (j : J) β†’ X₁ j ⟢ Xβ‚‚ j), (βˆ€ (j : J), W (f j)) β†’ W (Limits.Pi.map f)) :
                                        theorem CategoryTheory.MorphismProperty.IsStableUnderCoproductsOfShape.mk {C : Type u} [Category.{v, u} C] (W : MorphismProperty C) (J : Type u_1) [W.RespectsIso] (hW : βˆ€ (X₁ Xβ‚‚ : J β†’ C) [inst : Limits.HasCoproduct X₁] [inst_1 : Limits.HasCoproduct Xβ‚‚] (f : (j : J) β†’ X₁ j ⟢ Xβ‚‚ j), (βˆ€ (j : J), W (f j)) β†’ W (Limits.Sigma.map f)) :

                                        The condition that a property of morphisms is stable by finite products.

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                                          The condition that a property of morphisms is stable by finite coproducts.

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                                            The condition that a property of morphisms is stable by coproducts.

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                                              For P : MorphismProperty C, P.diagonal is a morphism property that holds for f : X ⟢ Y whenever P holds for X ⟢ Y xβ‚“ Y.

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                                                  If P is multiplicative and stable under base change, having the of-postcomp property w.r.t. Q is equivalent to Q implying P on the diagonal.

                                                  P.universally holds for a morphism f : X ⟢ Y iff P holds for all X Γ—[Y] Y' ⟢ Y'.

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                                                      theorem CategoryTheory.MorphismProperty.universally_mk' {C : Type u} [Category.{v, u} C] (P : MorphismProperty C) [P.RespectsIso] {X Y : C} (g : X ⟢ Y) (H : βˆ€ {T : C} (f : T ⟢ Y) [inst : Limits.HasPullback f g], P (Limits.pullback.fst f g)) :

                                                      P has pullbacks if for every f satisfying P, pullbacks of arbitrary morphisms along f exist.

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