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Mathlib.AlgebraicTopology.SimplicialObject.Basic

Simplicial objects in a category. #

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

Notation #

The following notations can be enabled via open Simplicial.

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

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    theorem CategoryTheory.instCategorySimplicialObject_comp_app (C : Type u) [Category.{v, u} C] {X✝ Y✝ Z✝ : Functor SimplexCategoryᵒᵖ C} (α : X✝ Y✝) (β : Y✝ Z✝) (X : SimplexCategoryᵒᵖ) :

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      X _⦋n⦌ denotes the nth-term of the simplicial object X

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        theorem CategoryTheory.SimplicialObject.hom_ext {C : Type u} [Category.{v, u} C] {X Y : SimplicialObject C} (f g : X Y) (h : ∀ (n : SimplexCategoryᵒᵖ), f.app n = g.app n) :
        f = g

        Face maps for a simplicial object.

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          Degeneracy maps for a simplicial object.

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

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              Isomorphisms from identities in ℕ.

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                theorem CategoryTheory.SimplicialObject.δ_comp_δ {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) {n : } {i j : Fin (n + 2)} (H : i j) :

                The generic case of the first simplicial identity

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

                The special case of the first simplicial identity

                theorem CategoryTheory.SimplicialObject.δ_comp_δ_self' {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) {n : } {j : Fin (n + 3)} {i : Fin (n + 2)} (H : j = i.castSucc) :
                theorem CategoryTheory.SimplicialObject.δ_comp_σ_of_le {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 1)} (H : i j.castSucc) :

                The second simplicial identity

                The first part of the third simplicial identity

                theorem CategoryTheory.SimplicialObject.δ_comp_σ_self'_assoc {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) {n : } {j : Fin (n + 2)} {i : Fin (n + 1)} (H : j = i.castSucc) {Z : C} (h : X.obj (Opposite.op (SimplexCategory.mk n)) Z) :

                The second part of the third simplicial identity

                theorem CategoryTheory.SimplicialObject.δ_comp_σ_succ'_assoc {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) {n : } {j : Fin (n + 2)} {i : Fin (n + 1)} (H : j = i.succ) {Z : C} (h : X.obj (Opposite.op (SimplexCategory.mk n)) Z) :
                theorem CategoryTheory.SimplicialObject.δ_comp_σ_of_gt {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 1)} (H : j.castSucc < i) :

                The fourth simplicial identity

                theorem CategoryTheory.SimplicialObject.δ_comp_σ_of_gt' {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : j.succ < i) :
                CategoryStruct.comp (X.σ j) (X.δ i) = CategoryStruct.comp (X.δ (i.pred )) (X.σ (j.castLT ))
                theorem CategoryTheory.SimplicialObject.δ_comp_σ_of_gt'_assoc {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : j.succ < i) {Z : C} (h : X.obj (Opposite.op (SimplexCategory.mk (n + 1))) Z) :
                theorem CategoryTheory.SimplicialObject.σ_comp_σ {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) {n : } {i j : Fin (n + 1)} (H : i j) :

                The fifth simplicial identity

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                theorem CategoryTheory.SimplicialObject.whiskering_obj_map_app (C : Type u) [Category.{v, u} C] (D : Type u_1) [Category.{u_2, u_1} D] (H : Functor C D) {X✝ Y✝ : Functor SimplexCategoryᵒᵖ C} (α : X✝ Y✝) (X : SimplexCategoryᵒᵖ) :
                (((whiskering C D).obj H).map α).app X = H.map (α.app X)
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                theorem CategoryTheory.SimplicialObject.whiskering_obj_obj_map (C : Type u) [Category.{v, u} C] (D : Type u_1) [Category.{u_2, u_1} D] (H : Functor C D) (F : Functor SimplexCategoryᵒᵖ C) {X✝ Y✝ : SimplexCategoryᵒᵖ} (f : X✝ Y✝) :
                (((whiskering C D).obj H).obj F).map f = H.map (F.map f)
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                theorem CategoryTheory.SimplicialObject.whiskering_map_app_app (C : Type u) [Category.{v, u} C] (D : Type u_1) [Category.{u_2, u_1} D] {X✝ Y✝ : Functor C D} (τ : X✝ Y✝) (F : Functor SimplexCategoryᵒᵖ C) (c : SimplexCategoryᵒᵖ) :
                (((whiskering C D).map τ).app F).app c = τ.app (F.obj c)

                Functor composition induces a functor on truncated simplicial objects.

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                  @[reducible, inline]

                  The constant simplicial object is the constant functor.

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                    theorem CategoryTheory.SimplicialObject.Augmented.hom_ext {C : Type u} [Category.{v, u} C] {X Y : 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.

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

                      Functor composition induces a functor on augmented simplicial objects.

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                        Functor composition induces a functor on augmented simplicial objects.

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                          theorem CategoryTheory.SimplicialObject.Augmented.whiskering_map_app_right (C : Type u) [Category.{v, u} C] (D : Type u') [Category.{v', u'} D] {X✝ Y✝ : Functor C D} (η : X✝ Y✝) (A : Augmented C) :
                          (((whiskering C D).map η).app A).right = η.app (point.obj A)
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                          theorem CategoryTheory.SimplicialObject.Augmented.whiskering_map_app_left (C : Type u) [Category.{v, u} C] (D : Type u') [Category.{v', u'} D] {X✝ Y✝ : Functor C D} (η : X✝ Y✝) (A : Augmented C) :
                          (((whiskering C D).map η).app A).left = whiskerLeft (drop.obj A) η

                          The constant augmented simplicial object functor.

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                            theorem CategoryTheory.SimplicialObject.Augmented.const_map_right {C : Type u} [Category.{v, u} C] {X✝ Y✝ : C} (f : X✝ Y✝) :

                            Augment a simplicial object with an object.

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                              theorem CategoryTheory.SimplicialObject.augment_right {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) (X₀ : C) (f : X.obj (Opposite.op (SimplexCategory.mk 0)) X₀) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryStruct.comp (X.map g₁.op) f = CategoryStruct.comp (X.map g₂.op) f) :
                              (X.augment X₀ f w).right = X₀
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                              theorem CategoryTheory.SimplicialObject.augment_left {C : Type u} [Category.{v, u} C] (X : SimplicialObject C) (X₀ : C) (f : X.obj (Opposite.op (SimplexCategory.mk 0)) X₀) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryStruct.comp (X.map g₁.op) f = CategoryStruct.comp (X.map g₂.op) f) :
                              (X.augment X₀ f w).left = X
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                              theorem CategoryTheory.instCategoryCosimplicialObject_comp_app (C : Type u) [Category.{v, u} C] {X✝ Y✝ Z✝ : Functor SimplexCategory C} (α : X✝ Y✝) (β : Y✝ Z✝) (X : SimplexCategory) :

                              X ^⦋n⦌ denotes the nth-term of the cosimplicial object X

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                                  theorem CategoryTheory.CosimplicialObject.hom_ext {C : Type u} [Category.{v, u} C] {X Y : CosimplicialObject C} (f g : X Y) (h : ∀ (n : SimplexCategory), f.app n = g.app n) :
                                  f = g

                                  Coface maps for a cosimplicial object.

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                                    Codegeneracy maps for a cosimplicial object.

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                                      Isomorphisms from identities in ℕ.

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                                        The generic case of the first cosimplicial identity

                                        theorem CategoryTheory.CosimplicialObject.δ_comp_δ' {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 3)} (H : i.castSucc < j) :
                                        theorem CategoryTheory.CosimplicialObject.δ_comp_δ'_assoc {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 3)} (H : i.castSucc < j) {Z : C} (h : X.obj (SimplexCategory.mk (n + 1 + 1)) Z) :
                                        theorem CategoryTheory.CosimplicialObject.δ_comp_δ'' {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : i j.castSucc) :
                                        CategoryStruct.comp (X.δ (i.castLT )) (X.δ j.succ) = CategoryStruct.comp (X.δ j) (X.δ i)
                                        theorem CategoryTheory.CosimplicialObject.δ_comp_δ''_assoc {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : i j.castSucc) {Z : C} (h : X.obj (SimplexCategory.mk (n + 1 + 1)) Z) :

                                        The special case of the first cosimplicial identity

                                        theorem CategoryTheory.CosimplicialObject.δ_comp_δ_self' {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 3)} (H : j = i.castSucc) :
                                        theorem CategoryTheory.CosimplicialObject.δ_comp_σ_of_le {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 1)} (H : i j.castSucc) :

                                        The second cosimplicial identity

                                        The first part of the third cosimplicial identity

                                        theorem CategoryTheory.CosimplicialObject.δ_comp_σ_self'_assoc {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {j : Fin (n + 2)} {i : Fin (n + 1)} (H : j = i.castSucc) {Z : C} (h : X.obj (SimplexCategory.mk n) Z) :

                                        The second part of the third cosimplicial identity

                                        theorem CategoryTheory.CosimplicialObject.δ_comp_σ_succ'_assoc {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {j : Fin (n + 2)} {i : Fin (n + 1)} (H : j = i.succ) {Z : C} (h : X.obj (SimplexCategory.mk n) Z) :
                                        theorem CategoryTheory.CosimplicialObject.δ_comp_σ_of_gt {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {i : Fin (n + 2)} {j : Fin (n + 1)} (H : j.castSucc < i) :

                                        The fourth cosimplicial identity

                                        theorem CategoryTheory.CosimplicialObject.δ_comp_σ_of_gt' {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : j.succ < i) :
                                        CategoryStruct.comp (X.δ i) (X.σ j) = CategoryStruct.comp (X.σ (j.castLT )) (X.δ (i.pred ))
                                        theorem CategoryTheory.CosimplicialObject.δ_comp_σ_of_gt'_assoc {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) {n : } {i : Fin (n + 3)} {j : Fin (n + 2)} (H : j.succ < i) {Z : C} (h : X.obj (SimplexCategory.mk (n + 1)) Z) :

                                        The fifth cosimplicial identity

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                                        theorem CategoryTheory.CosimplicialObject.whiskering_obj_obj_map (C : Type u) [Category.{v, u} C] (D : Type u_1) [Category.{u_2, u_1} D] (H : Functor C D) (F : Functor SimplexCategory C) {X✝ Y✝ : SimplexCategory} (f : X✝ Y✝) :
                                        (((whiskering C D).obj H).obj F).map f = H.map (F.map f)
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                                        theorem CategoryTheory.CosimplicialObject.whiskering_map_app_app (C : Type u) [Category.{v, u} C] (D : Type u_1) [Category.{u_2, u_1} D] {X✝ Y✝ : Functor C D} (τ : X✝ Y✝) (F : Functor SimplexCategory C) (c : SimplexCategory) :
                                        (((whiskering C D).map τ).app F).app c = τ.app (F.obj c)
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                                        theorem CategoryTheory.CosimplicialObject.whiskering_obj_map_app (C : Type u) [Category.{v, u} C] (D : Type u_1) [Category.{u_2, u_1} D] (H : Functor C D) {X✝ Y✝ : Functor SimplexCategory C} (α : X✝ Y✝) (X : SimplexCategory) :
                                        (((whiskering C D).obj H).map α).app X = H.map (α.app X)

                                        Functor composition induces a functor on truncated cosimplicial objects.

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                                          theorem CategoryTheory.CosimplicialObject.Truncated.whiskering_map_app_app (C : Type u) [Category.{v, u} C] {n : } (D : Type u_1) [Category.{u_2, u_1} D] {X✝ Y✝ : Functor C D} (τ : X✝ Y✝) (F : Functor (SimplexCategory.Truncated n) C) (c : SimplexCategory.Truncated n) :
                                          (((whiskering C D).map τ).app F).app c = τ.app (F.obj c)
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                                          theorem CategoryTheory.CosimplicialObject.Truncated.whiskering_obj_map_app (C : Type u) [Category.{v, u} C] {n : } (D : Type u_1) [Category.{u_2, u_1} D] (H : Functor C D) {X✝ Y✝ : Functor (SimplexCategory.Truncated n) C} (α : X✝ Y✝) (X : SimplexCategory.Truncated n) :
                                          (((whiskering C D).obj H).map α).app X = H.map (α.app X)
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                                          theorem CategoryTheory.CosimplicialObject.Truncated.whiskering_obj_obj_map (C : Type u) [Category.{v, u} C] {n : } (D : Type u_1) [Category.{u_2, u_1} D] (H : Functor C D) (F : Functor (SimplexCategory.Truncated n) C) {X✝ Y✝ : SimplexCategory.Truncated n} (f : X✝ Y✝) :
                                          (((whiskering C D).obj H).obj F).map f = H.map (F.map f)
                                          theorem CategoryTheory.CosimplicialObject.Augmented.hom_ext {C : Type u} [Category.{v, u} C] {X Y : 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.

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                                            Functor composition induces a functor on augmented cosimplicial objects.

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                                              Functor composition induces a functor on augmented cosimplicial objects.

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                                                theorem CategoryTheory.CosimplicialObject.Augmented.whiskering_map_app_right (C : Type u) [Category.{v, u} C] (D : Type u') [Category.{v', u'} D] {X✝ Y✝ : Functor C D} (η : X✝ Y✝) (A : Augmented C) :
                                                (((whiskering C D).map η).app A).right = whiskerLeft (drop.obj A) η
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                                                theorem CategoryTheory.CosimplicialObject.Augmented.whiskering_map_app_left (C : Type u) [Category.{v, u} C] (D : Type u') [Category.{v', u'} D] {X✝ Y✝ : Functor C D} (η : X✝ Y✝) (A : Augmented C) :
                                                (((whiskering C D).map η).app A).left = η.app (point.obj A)

                                                The constant augmented cosimplicial object functor.

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                                                  theorem CategoryTheory.CosimplicialObject.Augmented.const_map_left {C : Type u} [Category.{v, u} C] {X✝ Y✝ : C} (f : X✝ Y✝) :
                                                  (const.map f).left = f

                                                  Augment a cosimplicial object with an object.

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                                                    theorem CategoryTheory.CosimplicialObject.augment_hom_app {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) (X₀ : C) (f : X₀ X.obj (SimplexCategory.mk 0)) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryStruct.comp f (X.map g₁) = CategoryStruct.comp f (X.map g₂)) (x✝ : SimplexCategory) :
                                                    (X.augment X₀ f w).hom.app x✝ = CategoryStruct.comp f (X.map ((SimplexCategory.mk 0).const x✝ 0))
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                                                    theorem CategoryTheory.CosimplicialObject.augment_left {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) (X₀ : C) (f : X₀ X.obj (SimplexCategory.mk 0)) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryStruct.comp f (X.map g₁) = CategoryStruct.comp f (X.map g₂)) :
                                                    (X.augment X₀ f w).left = X₀
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                                                    theorem CategoryTheory.CosimplicialObject.augment_right {C : Type u} [Category.{v, u} C] (X : CosimplicialObject C) (X₀ : C) (f : X₀ X.obj (SimplexCategory.mk 0)) (w : ∀ (i : SimplexCategory) (g₁ g₂ : SimplexCategory.mk 0 i), CategoryStruct.comp f (X.map g₁) = 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.

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

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

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

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                                                            A functorial version of SimplicialObject.Augmented.rightOp.

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                                                              A functorial version of Cosimplicial_object.Augmented.leftOp.

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

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