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Define representations of monoids (UniMath#765)
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src/category-theory/dependent-products-of-categories.lagda.md
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# Dependent products of categories | ||
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```agda | ||
module category-theory.dependent-products-of-categories where | ||
``` | ||
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<details><summary>Imports</summary> | ||
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```agda | ||
open import category-theory.categories | ||
open import category-theory.dependent-products-of-precategories | ||
open import category-theory.isomorphisms-in-categories | ||
open import category-theory.precategories | ||
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open import foundation.dependent-pair-types | ||
open import foundation.equivalences | ||
open import foundation.function-extensionality | ||
open import foundation.function-types | ||
open import foundation.functoriality-dependent-function-types | ||
open import foundation.identity-types | ||
open import foundation.sets | ||
open import foundation.universe-levels | ||
``` | ||
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</details> | ||
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## Idea | ||
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Given a family of [categories](category-theory.categories.md) `Cᵢ` indexed by | ||
`i : I`, the dependent product type `Π(i : I), Cᵢ` is a category consisting of | ||
functions taking `i : I` to an object of `Cᵢ`. Every component of the structure | ||
is given pointwise. | ||
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## Definition | ||
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```agda | ||
module _ | ||
{l1 l2 l3 : Level} (I : UU l1) (C : I → Category l2 l3) | ||
where | ||
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precategory-Π-Category : Precategory (l1 ⊔ l2) (l1 ⊔ l3) | ||
precategory-Π-Category = Π-Precategory I (precategory-Category ∘ C) | ||
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abstract | ||
is-category-precategory-Π-Category : | ||
is-category-Precategory precategory-Π-Category | ||
is-category-precategory-Π-Category x y = | ||
is-equiv-htpy-equiv | ||
( equiv-iso-Π-fiberwise-iso-Precategory I (precategory-Category ∘ C) ∘e | ||
equiv-Π-equiv-family | ||
( λ i → extensionality-obj-Category (C i) (x i) (y i)) ∘e | ||
equiv-funext) | ||
( λ {refl → refl}) | ||
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Π-Category : Category (l1 ⊔ l2) (l1 ⊔ l3) | ||
pr1 Π-Category = Π-Precategory I (precategory-Category ∘ C) | ||
pr2 Π-Category = is-category-precategory-Π-Category | ||
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obj-Π-Category : UU (l1 ⊔ l2) | ||
obj-Π-Category = obj-Category Π-Category | ||
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hom-Π-Category : | ||
obj-Π-Category → obj-Π-Category → Set (l1 ⊔ l3) | ||
hom-Π-Category = hom-Category Π-Category | ||
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type-hom-Π-Category : | ||
obj-Π-Category → obj-Π-Category → UU (l1 ⊔ l3) | ||
type-hom-Π-Category = type-hom-Category Π-Category | ||
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comp-hom-Π-Category : | ||
{x y z : obj-Π-Category} → | ||
type-hom-Π-Category y z → | ||
type-hom-Π-Category x y → | ||
type-hom-Π-Category x z | ||
comp-hom-Π-Category = comp-hom-Category Π-Category | ||
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associative-comp-hom-Π-Category : | ||
{x y z w : obj-Π-Category} | ||
(h : type-hom-Π-Category z w) | ||
(g : type-hom-Π-Category y z) | ||
(f : type-hom-Π-Category x y) → | ||
( comp-hom-Π-Category (comp-hom-Π-Category h g) f) = | ||
( comp-hom-Π-Category h (comp-hom-Π-Category g f)) | ||
associative-comp-hom-Π-Category = | ||
associative-comp-hom-Category Π-Category | ||
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associative-composition-structure-Π-Category : | ||
associative-composition-structure-Set hom-Π-Category | ||
associative-composition-structure-Π-Category = | ||
associative-composition-structure-Category Π-Category | ||
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id-hom-Π-Category : | ||
{x : obj-Π-Category} → type-hom-Π-Category x x | ||
id-hom-Π-Category = id-hom-Category Π-Category | ||
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left-unit-law-comp-hom-Π-Category : | ||
{x y : obj-Π-Category} | ||
(f : type-hom-Π-Category x y) → | ||
comp-hom-Π-Category id-hom-Π-Category f = f | ||
left-unit-law-comp-hom-Π-Category = | ||
left-unit-law-comp-hom-Category Π-Category | ||
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right-unit-law-comp-hom-Π-Category : | ||
{x y : obj-Π-Category} (f : type-hom-Π-Category x y) → | ||
comp-hom-Π-Category f id-hom-Π-Category = f | ||
right-unit-law-comp-hom-Π-Category = | ||
right-unit-law-comp-hom-Category Π-Category | ||
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is-unital-Π-Category : | ||
is-unital-composition-structure-Set | ||
hom-Π-Category | ||
associative-composition-structure-Π-Category | ||
is-unital-Π-Category = is-unital-composition-structure-Category Π-Category | ||
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extensionality-obj-Π-Category : | ||
(x y : obj-Category Π-Category) → (x = y) ≃ iso-Category Π-Category x y | ||
extensionality-obj-Π-Category = extensionality-obj-Category Π-Category | ||
``` | ||
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## Properties | ||
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### Isomorphisms in the dependent product category are fiberwise isomorphisms | ||
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```agda | ||
module _ | ||
{l1 l2 l3 : Level} (I : UU l1) (C : I → Category l2 l3) | ||
{x y : obj-Π-Category I C} | ||
where | ||
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is-fiberwise-iso-is-iso-Π-Category : | ||
(f : type-hom-Π-Category I C x y) → | ||
is-iso-Category (Π-Category I C) f → | ||
(i : I) → is-iso-Category (C i) (f i) | ||
is-fiberwise-iso-is-iso-Π-Category = | ||
is-fiberwise-iso-is-iso-Π-Precategory I (precategory-Category ∘ C) | ||
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fiberwise-iso-iso-Π-Category : | ||
iso-Category (Π-Category I C) x y → | ||
(i : I) → iso-Category (C i) (x i) (y i) | ||
fiberwise-iso-iso-Π-Category = | ||
fiberwise-iso-iso-Π-Precategory I (precategory-Category ∘ C) | ||
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is-iso-Π-is-fiberwise-iso-Category : | ||
(f : type-hom-Π-Category I C x y) → | ||
((i : I) → is-iso-Category (C i) (f i)) → | ||
is-iso-Category (Π-Category I C) f | ||
is-iso-Π-is-fiberwise-iso-Category = | ||
is-iso-Π-is-fiberwise-iso-Precategory I (precategory-Category ∘ C) | ||
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iso-Π-fiberwise-iso-Category : | ||
((i : I) → iso-Category (C i) (x i) (y i)) → | ||
iso-Category (Π-Category I C) x y | ||
iso-Π-fiberwise-iso-Category = | ||
iso-Π-fiberwise-iso-Precategory I (precategory-Category ∘ C) | ||
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is-equiv-is-fiberwise-iso-is-iso-Π-Category : | ||
(f : type-hom-Π-Category I C x y) → | ||
is-equiv (is-fiberwise-iso-is-iso-Π-Category f) | ||
is-equiv-is-fiberwise-iso-is-iso-Π-Category = | ||
is-equiv-is-fiberwise-iso-is-iso-Π-Precategory I (precategory-Category ∘ C) | ||
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equiv-is-fiberwise-iso-is-iso-Π-Category : | ||
(f : type-hom-Π-Category I C x y) → | ||
( is-iso-Category (Π-Category I C) f) ≃ | ||
( (i : I) → is-iso-Category (C i) (f i)) | ||
equiv-is-fiberwise-iso-is-iso-Π-Category = | ||
equiv-is-fiberwise-iso-is-iso-Π-Precategory I (precategory-Category ∘ C) | ||
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is-equiv-is-iso-Π-is-fiberwise-iso-Category : | ||
(f : type-hom-Π-Category I C x y) → | ||
is-equiv (is-iso-Π-is-fiberwise-iso-Category f) | ||
is-equiv-is-iso-Π-is-fiberwise-iso-Category = | ||
is-equiv-is-iso-Π-is-fiberwise-iso-Precategory I (precategory-Category ∘ C) | ||
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equiv-is-iso-Π-is-fiberwise-iso-Category : | ||
( f : type-hom-Π-Category I C x y) → | ||
( (i : I) → is-iso-Category (C i) (f i)) ≃ | ||
( is-iso-Category (Π-Category I C) f) | ||
equiv-is-iso-Π-is-fiberwise-iso-Category = | ||
equiv-is-iso-Π-is-fiberwise-iso-Precategory I (precategory-Category ∘ C) | ||
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is-equiv-fiberwise-iso-iso-Π-Category : | ||
is-equiv fiberwise-iso-iso-Π-Category | ||
is-equiv-fiberwise-iso-iso-Π-Category = | ||
is-equiv-fiberwise-iso-iso-Π-Precategory I (precategory-Category ∘ C) | ||
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equiv-fiberwise-iso-iso-Π-Category : | ||
( iso-Category (Π-Category I C) x y) ≃ | ||
( (i : I) → iso-Category (C i) (x i) (y i)) | ||
equiv-fiberwise-iso-iso-Π-Category = | ||
equiv-fiberwise-iso-iso-Π-Precategory I (precategory-Category ∘ C) | ||
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is-equiv-iso-Π-fiberwise-iso-Category : | ||
is-equiv iso-Π-fiberwise-iso-Category | ||
is-equiv-iso-Π-fiberwise-iso-Category = | ||
is-equiv-iso-Π-fiberwise-iso-Precategory I (precategory-Category ∘ C) | ||
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equiv-iso-Π-fiberwise-iso-Category : | ||
( (i : I) → iso-Category (C i) (x i) (y i)) ≃ | ||
( iso-Category (Π-Category I C) x y) | ||
equiv-iso-Π-fiberwise-iso-Category = | ||
equiv-iso-Π-fiberwise-iso-Precategory I (precategory-Category ∘ C) | ||
``` |
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