Documentation

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 following notations can be enabled via open CategoryTheory.SimplicialObject.Truncated.

@[simp]
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) :

Pretty printer defined by notation3 command.

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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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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

@[simp]
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)
@[simp]
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)
@[simp]
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)
@[simp]
@[simp]

For X : Truncated C n and m ≤ n, X _⦋m⦌ₙ is the m-th term of X. The proof p : m ≤ n can also be provided using the syntax X _⦋m, p⦌ₙ.

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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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@[simp]

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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@[simp]
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
@[simp]
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)

The constant augmented simplicial object functor.

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@[simp]
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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@[simp]
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
@[simp]
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
@[simp]
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) :

Pretty printer defined by notation3 command.

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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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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

@[simp]
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)
@[simp]
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)
@[simp]
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)
@[simp]
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)
@[simp]
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)
@[simp]
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)

For X : Truncated C n and m ≤ n, X ^⦋m⦌ₙ is the m-th term of X. The proof p : m ≤ n can also be provided using the syntax X ^⦋m, p⦌ₙ.

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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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@[simp]

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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@[simp]
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)
@[simp]
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

The constant augmented cosimplicial object functor.

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@[simp]
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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@[simp]
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
@[simp]
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))
@[simp]
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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