Documentation

Mathlib.CategoryTheory.ObjectProperty.ColimitsOfShape

Objects that are colimits of objects satisfying a certain property #

Given a property of objects P : ObjectProperty C and a category J, we introduce two properties of objects P.strictColimitsOfShape J and P.colimitsOfShape J. The former contains exactly the objects of the form colimit F for any functor F : J ⥤ C that has a colimit and such that F.obj j satisfies P for any j, while the latter contains all the objects that are isomorphic to these "chosen" objects colimit F.

Under certain circumstances, the type of objects satisfying P.strictColimitsOfShape J is small: the main reason this variant is introduced is to deduce that the full subcategory of P.colimitsOfShape J is essentially small.

By requiring P.colimitsOfShape J ≤ P, we introduce a typeclass P.IsClosedUnderColimitsOfShape J.

We also show that colimitsOfShape in a category C is related to limitsOfShape in the opposite category Cᵒᵖ and vice versa.

TODO #

The property of objects that are equal to colimit F for some functor F : J ⥤ C where all F.obj j satisfy P.

Instances For
    structure CategoryTheory.ObjectProperty.ColimitOfShape {C : Type u_1} [Category.{v_1, u_1} C] (P : ObjectProperty C) (J : Type u') [Category.{v', u'} J] (X : C) extends CategoryTheory.Limits.ColimitPresentation J X :
    Type (max (max (max u' u_1) v') v_1)

    A structure expressing that X : C is the colimit of a functor diag : J ⥤ C such that P (diag.obj j) holds for all j.

    Instances For
      noncomputable def CategoryTheory.ObjectProperty.ColimitOfShape.colimit {C : Type u_1} [Category.{v_1, u_1} C] {P : ObjectProperty C} {J : Type u'} [Category.{v', u'} J] (F : Functor J C) [Limits.HasColimit F] (hF : ∀ (j : J), P (F.obj j)) :

      If F : J ⥤ C is a functor that has a colimit and is such that for all j, F.obj j satisfies a property P, then this structure expresses that colimit F is indeed a colimit of objects satisfying P.

      Equations
        Instances For

          If X is a colimit indexed by J of objects satisfying a property P, then any object that is isomorphic to X also is.

          Equations
            Instances For

              If X is a colimit indexed by J of objects satisfying a property P, it is also a colimit indexed by J of objects satisfying Q if P ≤ Q.

              Equations
                Instances For
                  noncomputable def CategoryTheory.ObjectProperty.ColimitOfShape.reindex {C : Type u_1} [Category.{v_1, u_1} C] {P : ObjectProperty C} {J : Type u'} [Category.{v', u'} J] {J' : Type u''} [Category.{v'', u''} J'] {X : C} (h : P.ColimitOfShape J X) (G : Functor J' J) [G.Final] :

                  Change the index category for ObjectProperty.ColimitOfShape.

                  Equations
                    Instances For

                      Given P : ObjectProperty C, and a presentation P.ColimitOfShape J X of an object X : C, this is the induced functor J ⥤ CostructuredArrow P.ι X.

                      Equations
                        Instances For

                          The property of objects that are the point of a colimit cocone for a functor F : J ⥤ C where all objects F.obj j satisfy P.

                          Equations
                            Instances For

                              A property of objects satisfies P.IsClosedUnderColimitsOfShape J if it is stable by colimits of shape J.

                              Instances
                                @[deprecated CategoryTheory.ObjectProperty.IsClosedUnderColimitsOfShape (since := "2025-09-22")]

                                Alias of CategoryTheory.ObjectProperty.IsClosedUnderColimitsOfShape.


                                A property of objects satisfies P.IsClosedUnderColimitsOfShape J if it is stable by colimits of shape J.

                                Equations
                                  Instances For
                                    @[deprecated CategoryTheory.ObjectProperty.IsClosedUnderColimitsOfShape.mk' (since := "2025-09-22")]

                                    Alias of CategoryTheory.ObjectProperty.IsClosedUnderColimitsOfShape.mk'.

                                    @[deprecated CategoryTheory.ObjectProperty.prop_colimit (since := "2025-09-22")]

                                    Alias of CategoryTheory.ObjectProperty.prop_colimit.