Documentation

Mathlib.AlgebraicTopology.SimplicialObject

Simplicial objects in a category. #

A simplicial object in a category C is a C-valued presheaf on SimplexCategory. (Similarly a cosimplicial object is functor SimplexCategory ⥤ C.)

Use the notation X _[n] in the Simplicial locale to obtain the n-th term of a (co)simplicial object X, where n is a natural number.

The category of simplicial objects valued in a category C. This is the category of contravariant functors from SimplexCategory to C.

Equations
Instances For

    Pretty printer defined by notation3 command.

    Equations
    • One or more equations did not get rendered due to their size.
    Instances For

      X _[n] denotes the nth-term of the simplicial object X

      Equations
      • One or more equations did not get rendered due to their size.
      Instances For

        Face maps for a simplicial object.

        Equations
        Instances For

          Degeneracy maps for a simplicial object.

          Equations
          Instances For

            The diagonal of a simplex is the long edge of the simplex.

            Equations
            Instances For

              Isomorphisms from identities in ℕ.

              Equations
              Instances For

                The generic case of the first simplicial identity

                theorem CategoryTheory.SimplicialObject.δ_comp_δ' {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 3)} (H : i.castSucc < j) :
                CategoryTheory.CategoryStruct.comp (X j) (X i) = CategoryTheory.CategoryStruct.comp (X i.castSucc) (X (j.pred ))
                theorem CategoryTheory.SimplicialObject.δ_comp_δ'' {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : i j.castSucc) :
                CategoryTheory.CategoryStruct.comp (X j.succ) (X (i.castLT )) = CategoryTheory.CategoryStruct.comp (X i) (X j)

                The special case of the first simplicial identity

                theorem CategoryTheory.SimplicialObject.δ_comp_σ_of_le {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 1)} (H : i j.castSucc) :
                CategoryTheory.CategoryStruct.comp (X j.succ) (X i.castSucc) = CategoryTheory.CategoryStruct.comp (X i) (X j)

                The second simplicial identity

                theorem CategoryTheory.SimplicialObject.δ_comp_σ_of_gt {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 1)} (H : j.castSucc < i) :
                CategoryTheory.CategoryStruct.comp (X j.castSucc) (X i.succ) = CategoryTheory.CategoryStruct.comp (X i) (X j)

                The fourth simplicial identity

                theorem CategoryTheory.SimplicialObject.δ_comp_σ_of_gt' {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : j.succ < i) :
                CategoryTheory.CategoryStruct.comp (X j) (X i) = CategoryTheory.CategoryStruct.comp (X (i.pred )) (X (j.castLT ))

                The fifth simplicial identity

                @[reducible, inline]

                The n-skeleton as a functor SimplicialObject.Truncated C n ⥤ SimplicialObject C.

                Equations
                Instances For
                  @[reducible, inline]

                  The n-coskeleton as a functor SimplicialObject.Truncated C n ⥤ SimplicialObject C.

                  Equations
                  Instances For

                    The adjunction between the n-skeleton and n-truncation.

                    Equations
                    Instances For

                      The adjunction between n-truncation and the n-coskeleton.

                      Equations
                      Instances For
                        instance CategoryTheory.SimplicialObject.Truncated.cosk_reflective {C : Type u} [CategoryTheory.Category.{v, u} C] (n : ) [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasRightKanExtension F] [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasPointwiseRightKanExtension F] :
                        Equations
                        • =
                        instance CategoryTheory.SimplicialObject.Truncated.sk_coreflective {C : Type u} [CategoryTheory.Category.{v, u} C] (n : ) [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasLeftKanExtension F] [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasPointwiseLeftKanExtension F] :
                        Equations
                        • =
                        noncomputable def CategoryTheory.SimplicialObject.Truncated.cosk.fullyFaithful {C : Type u} [CategoryTheory.Category.{v, u} C] (n : ) [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasRightKanExtension F] [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasPointwiseRightKanExtension F] :

                        Since Truncated.inclusion is fully faithful, so is right Kan extension along it.

                        Equations
                        Instances For
                          instance CategoryTheory.SimplicialObject.Truncated.cosk.full {C : Type u} [CategoryTheory.Category.{v, u} C] (n : ) [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasRightKanExtension F] [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasPointwiseRightKanExtension F] :
                          Equations
                          • =
                          instance CategoryTheory.SimplicialObject.Truncated.cosk.faithful {C : Type u} [CategoryTheory.Category.{v, u} C] (n : ) [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasRightKanExtension F] [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasPointwiseRightKanExtension F] :
                          Equations
                          • =
                          noncomputable def CategoryTheory.SimplicialObject.Truncated.sk.fullyFaithful {C : Type u} [CategoryTheory.Category.{v, u} C] (n : ) [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasLeftKanExtension F] [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasPointwiseLeftKanExtension F] :

                          Since Truncated.inclusion is fully faithful, so is left Kan extension along it.

                          Equations
                          Instances For
                            instance CategoryTheory.SimplicialObject.Truncated.sk.full {C : Type u} [CategoryTheory.Category.{v, u} C] (n : ) [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasLeftKanExtension F] [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasPointwiseLeftKanExtension F] :
                            Equations
                            • =
                            instance CategoryTheory.SimplicialObject.Truncated.sk.faithful {C : Type u} [CategoryTheory.Category.{v, u} C] (n : ) [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasLeftKanExtension F] [∀ (F : CategoryTheory.Functor (SimplexCategory.Truncated n)ᵒᵖ C), SimplexCategory.Truncated.inclusion.op.HasPointwiseLeftKanExtension F] :
                            Equations
                            • =
                            theorem CategoryTheory.SimplicialObject.Augmented.hom_ext {C : Type u} [CategoryTheory.Category.{v, u} C] {X Y : CategoryTheory.SimplicialObject.Augmented C} (f g : X Y) (h₁ : f.left = g.left) (h₂ : f.right = g.right) :
                            f = g
                            @[simp]

                            The functor from augmented objects to arrows.

                            Equations
                            • One or more equations did not get rendered due to their size.
                            Instances For
                              @[simp]
                              theorem CategoryTheory.SimplicialObject.Augmented.toArrow_map_left {C : Type u} [CategoryTheory.Category.{v, u} C] {X✝ Y✝ : CategoryTheory.SimplicialObject.Augmented C} (η : X✝ Y✝) :
                              (CategoryTheory.SimplicialObject.Augmented.toArrow.map η).left = (CategoryTheory.SimplicialObject.Augmented.drop.map η).app (Opposite.op (SimplexCategory.mk 0))
                              @[simp]
                              theorem CategoryTheory.SimplicialObject.Augmented.toArrow_obj_right {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject.Augmented C) :
                              (CategoryTheory.SimplicialObject.Augmented.toArrow.obj X).right = CategoryTheory.SimplicialObject.Augmented.point.obj X
                              @[simp]
                              theorem CategoryTheory.SimplicialObject.Augmented.toArrow_obj_hom {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject.Augmented C) :
                              (CategoryTheory.SimplicialObject.Augmented.toArrow.obj X).hom = X.hom.app (Opposite.op (SimplexCategory.mk 0))
                              @[simp]
                              theorem CategoryTheory.SimplicialObject.Augmented.toArrow_obj_left {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject.Augmented C) :
                              (CategoryTheory.SimplicialObject.Augmented.toArrow.obj X).left = (CategoryTheory.SimplicialObject.Augmented.drop.obj X).obj (Opposite.op (SimplexCategory.mk 0))
                              @[simp]
                              theorem CategoryTheory.SimplicialObject.Augmented.toArrow_map_right {C : Type u} [CategoryTheory.Category.{v, u} C] {X✝ Y✝ : CategoryTheory.SimplicialObject.Augmented C} (η : X✝ Y✝) :
                              (CategoryTheory.SimplicialObject.Augmented.toArrow.map η).right = CategoryTheory.SimplicialObject.Augmented.point.map η
                              theorem CategoryTheory.SimplicialObject.Augmented.w₀ {C : Type u} [CategoryTheory.Category.{v, u} C] {X Y : CategoryTheory.SimplicialObject.Augmented C} (f : X Y) :
                              CategoryTheory.CategoryStruct.comp ((CategoryTheory.SimplicialObject.Augmented.drop.map f).app (Opposite.op (SimplexCategory.mk 0))) (Y.hom.app (Opposite.op (SimplexCategory.mk 0))) = CategoryTheory.CategoryStruct.comp (X.hom.app (Opposite.op (SimplexCategory.mk 0))) (CategoryTheory.SimplicialObject.Augmented.point.map f)

                              The compatibility of a morphism with the augmentation, on 0-simplices

                              Functor composition induces a functor on augmented simplicial objects.

                              Equations
                              • One or more equations did not get rendered due to their size.
                              Instances For

                                Functor composition induces a functor on augmented simplicial objects.

                                Equations
                                • One or more equations did not get rendered due to their size.
                                Instances For
                                  @[simp]
                                  theorem CategoryTheory.SimplicialObject.Augmented.whiskering_map_app_right (C : Type u) [CategoryTheory.Category.{v, u} C] (D : Type u') [CategoryTheory.Category.{v', u'} D] {X✝ Y✝ : CategoryTheory.Functor C D} (η : X✝ Y✝) (A : CategoryTheory.SimplicialObject.Augmented C) :
                                  (((CategoryTheory.SimplicialObject.Augmented.whiskering C D).map η).app A).right = η.app (CategoryTheory.SimplicialObject.Augmented.point.obj A)

                                  Augment a simplicial object with an object.

                                  Equations
                                  • One or more equations did not get rendered due to their size.
                                  Instances For
                                    @[simp]
                                    theorem CategoryTheory.SimplicialObject.augment_right {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject C) (X₀ : C) (f : X.obj (Opposite.op (SimplexCategory.mk 0)) X₀) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryTheory.CategoryStruct.comp (X.map g₁.op) f = CategoryTheory.CategoryStruct.comp (X.map g₂.op) f) :
                                    (X.augment X₀ f w).right = X₀
                                    @[simp]
                                    theorem CategoryTheory.SimplicialObject.augment_left {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject C) (X₀ : C) (f : X.obj (Opposite.op (SimplexCategory.mk 0)) X₀) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryTheory.CategoryStruct.comp (X.map g₁.op) f = CategoryTheory.CategoryStruct.comp (X.map g₂.op) f) :
                                    (X.augment X₀ f w).left = X
                                    @[simp]
                                    theorem CategoryTheory.SimplicialObject.augment_hom_app {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject C) (X₀ : C) (f : X.obj (Opposite.op (SimplexCategory.mk 0)) X₀) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryTheory.CategoryStruct.comp (X.map g₁.op) f = CategoryTheory.CategoryStruct.comp (X.map g₂.op) f) (x✝ : SimplexCategoryᵒᵖ) :
                                    (X.augment X₀ f w).hom.app x✝ = CategoryTheory.CategoryStruct.comp (X.map ((SimplexCategory.mk 0).const (Opposite.unop x✝) 0).op) f

                                    X _[n] denotes the nth-term of the cosimplicial object X

                                    Equations
                                    • One or more equations did not get rendered due to their size.
                                    Instances For

                                      Coface maps for a cosimplicial object.

                                      Equations
                                      Instances For

                                        Codegeneracy maps for a cosimplicial object.

                                        Equations
                                        Instances For

                                          Isomorphisms from identities in ℕ.

                                          Equations
                                          Instances For

                                            The generic case of the first cosimplicial identity

                                            theorem CategoryTheory.CosimplicialObject.δ_comp_δ' {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 3)} (H : i.castSucc < j) :
                                            CategoryTheory.CategoryStruct.comp (X i) (X j) = CategoryTheory.CategoryStruct.comp (X (j.pred )) (X i.castSucc)
                                            theorem CategoryTheory.CosimplicialObject.δ_comp_δ'' {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : i j.castSucc) :
                                            CategoryTheory.CategoryStruct.comp (X (i.castLT )) (X j.succ) = CategoryTheory.CategoryStruct.comp (X j) (X i)

                                            The special case of the first cosimplicial identity

                                            theorem CategoryTheory.CosimplicialObject.δ_comp_σ_of_le {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 1)} (H : i j.castSucc) :
                                            CategoryTheory.CategoryStruct.comp (X i.castSucc) (X j.succ) = CategoryTheory.CategoryStruct.comp (X j) (X i)

                                            The second cosimplicial identity

                                            The first part of the third cosimplicial identity

                                            theorem CategoryTheory.CosimplicialObject.δ_comp_σ_of_gt {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 1)} (H : j.castSucc < i) :
                                            CategoryTheory.CategoryStruct.comp (X i.succ) (X j.castSucc) = CategoryTheory.CategoryStruct.comp (X j) (X i)

                                            The fourth cosimplicial identity

                                            theorem CategoryTheory.CosimplicialObject.δ_comp_σ_of_gt' {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : j.succ < i) :
                                            CategoryTheory.CategoryStruct.comp (X i) (X j) = CategoryTheory.CategoryStruct.comp (X (j.castLT )) (X (i.pred ))

                                            The fifth cosimplicial identity

                                            theorem CategoryTheory.CosimplicialObject.Augmented.hom_ext {C : Type u} [CategoryTheory.Category.{v, u} C] {X Y : CategoryTheory.CosimplicialObject.Augmented C} (f g : X Y) (h₁ : f.left = g.left) (h₂ : f.right = g.right) :
                                            f = g

                                            The functor from augmented objects to arrows.

                                            Equations
                                            • One or more equations did not get rendered due to their size.
                                            Instances For
                                              @[simp]
                                              theorem CategoryTheory.CosimplicialObject.Augmented.toArrow_obj_hom {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject.Augmented C) :
                                              (CategoryTheory.CosimplicialObject.Augmented.toArrow.obj X).hom = X.hom.app (SimplexCategory.mk 0)
                                              @[simp]
                                              theorem CategoryTheory.CosimplicialObject.Augmented.toArrow_obj_left {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject.Augmented C) :
                                              (CategoryTheory.CosimplicialObject.Augmented.toArrow.obj X).left = X.left
                                              @[simp]
                                              theorem CategoryTheory.CosimplicialObject.Augmented.toArrow_map_left {C : Type u} [CategoryTheory.Category.{v, u} C] {X✝ Y✝ : CategoryTheory.CosimplicialObject.Augmented C} (η : X✝ Y✝) :
                                              (CategoryTheory.CosimplicialObject.Augmented.toArrow.map η).left = η.left
                                              @[simp]
                                              theorem CategoryTheory.CosimplicialObject.Augmented.toArrow_obj_right {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject.Augmented C) :
                                              (CategoryTheory.CosimplicialObject.Augmented.toArrow.obj X).right = X.right.obj (SimplexCategory.mk 0)
                                              @[simp]
                                              theorem CategoryTheory.CosimplicialObject.Augmented.toArrow_map_right {C : Type u} [CategoryTheory.Category.{v, u} C] {X✝ Y✝ : CategoryTheory.CosimplicialObject.Augmented C} (η : X✝ Y✝) :
                                              (CategoryTheory.CosimplicialObject.Augmented.toArrow.map η).right = η.right.app (SimplexCategory.mk 0)

                                              Functor composition induces a functor on augmented cosimplicial objects.

                                              Equations
                                              • One or more equations did not get rendered due to their size.
                                              Instances For

                                                Functor composition induces a functor on augmented cosimplicial objects.

                                                Equations
                                                • One or more equations did not get rendered due to their size.
                                                Instances For
                                                  @[simp]
                                                  theorem CategoryTheory.CosimplicialObject.Augmented.whiskering_map_app_left (C : Type u) [CategoryTheory.Category.{v, u} C] (D : Type u') [CategoryTheory.Category.{v', u'} D] {X✝ Y✝ : CategoryTheory.Functor C D} (η : X✝ Y✝) (A : CategoryTheory.CosimplicialObject.Augmented C) :
                                                  (((CategoryTheory.CosimplicialObject.Augmented.whiskering C D).map η).app A).left = η.app (CategoryTheory.CosimplicialObject.Augmented.point.obj A)

                                                  Augment a cosimplicial object with an object.

                                                  Equations
                                                  • One or more equations did not get rendered due to their size.
                                                  Instances For
                                                    @[simp]
                                                    theorem CategoryTheory.CosimplicialObject.augment_hom_app {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject C) (X₀ : C) (f : X₀ X.obj (SimplexCategory.mk 0)) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryTheory.CategoryStruct.comp f (X.map g₁) = CategoryTheory.CategoryStruct.comp f (X.map g₂)) (x✝ : SimplexCategory) :
                                                    (X.augment X₀ f w).hom.app x✝ = CategoryTheory.CategoryStruct.comp f (X.map ((SimplexCategory.mk 0).const x✝ 0))
                                                    @[simp]
                                                    theorem CategoryTheory.CosimplicialObject.augment_left {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject C) (X₀ : C) (f : X₀ X.obj (SimplexCategory.mk 0)) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryTheory.CategoryStruct.comp f (X.map g₁) = CategoryTheory.CategoryStruct.comp f (X.map g₂)) :
                                                    (X.augment X₀ f w).left = X₀
                                                    @[simp]
                                                    theorem CategoryTheory.CosimplicialObject.augment_right {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.CosimplicialObject C) (X₀ : C) (f : X₀ X.obj (SimplexCategory.mk 0)) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryTheory.CategoryStruct.comp f (X.map g₁) = CategoryTheory.CategoryStruct.comp f (X.map g₂)) :
                                                    (X.augment X₀ f w).right = X
                                                    @[simp]

                                                    Construct an augmented cosimplicial object in the opposite category from an augmented simplicial object.

                                                    Equations
                                                    Instances For
                                                      @[simp]
                                                      theorem CategoryTheory.SimplicialObject.Augmented.rightOp_right_map {C : Type u} [CategoryTheory.Category.{v, u} C] (X : CategoryTheory.SimplicialObject.Augmented C) {X✝ Y✝ : SimplexCategory} (f : X✝ Y✝) :
                                                      X.rightOp.right.map f = (X.left.map f.op).op

                                                      Construct an augmented simplicial object from an augmented cosimplicial object in the opposite category.

                                                      Equations
                                                      Instances For
                                                        @[simp]

                                                        Converting an augmented simplicial object to an augmented cosimplicial object and back is isomorphic to the given object.

                                                        Equations
                                                        Instances For

                                                          Converting an augmented cosimplicial object to an augmented simplicial object and back is isomorphic to the given object.

                                                          Equations
                                                          Instances For

                                                            A functorial version of Cosimplicial_object.Augmented.leftOp.

                                                            Equations
                                                            • One or more equations did not get rendered due to their size.
                                                            Instances For

                                                              The contravariant categorical equivalence between augmented simplicial objects and augmented cosimplicial objects in the opposite category.

                                                              Equations
                                                              • One or more equations did not get rendered due to their size.
                                                              Instances For