diff --git a/src/simplicial-hott/13-yoneda-geodesic.rzk.md b/src/simplicial-hott/13-yoneda-geodesic.rzk.md index 146c07f..e71d689 100644 --- a/src/simplicial-hott/13-yoneda-geodesic.rzk.md +++ b/src/simplicial-hott/13-yoneda-geodesic.rzk.md @@ -54,6 +54,163 @@ naturality-covariant-fiberwise-transformation naturality is automatic. ( is-contravariant-representable-is-pre-∞-category A is-pre-∞-category-A b) ( ϕ) ( f) + +-- Same as the above but without the contravariant transport. +-- This unfolds a composition triangle to a square with an identity component +#def id-codomain-square + ( A : U) + ( is-pre-∞-category-A : is-pre-∞-category A) + ( x y a : A) + ( f : hom A x y) + ( v : hom A y a) + : ( t : Δ¹) → hom A (f t) a + := \ t s → + recOR + ( s ≤ t ↦ + ( witness-comp-is-pre-∞-category A is-pre-∞-category-A x y a f v) + ( t , s) + , t ≤ s ↦ + ( comp-id-witness A x a + ( comp-is-pre-∞-category A is-pre-∞-category-A x y a f v)) (s , t)) + +-- We apply the transformation phi to the square just constructed. +#def transformation-id-codomain-square + ( A : U) + ( is-pre-∞-category-A : is-pre-∞-category A) + ( a b x y : A) + ( f : hom A x y) + ( v : hom A y a) + ( ϕ : (z : A) → hom A z a → hom A z b) + : ( t : Δ¹) → hom A (f t) b + := \ t → ϕ (f t) (\ s → id-codomain-square A is-pre-∞-category-A x y a f v t s) + +-- This extracts the diagonal composite of the square. +#def diagonal-transformation-id-codomain-square + ( A : U) + ( is-pre-∞-category-A : is-pre-∞-category A) + ( a b x y : A) + ( f : hom A x y) + ( v : hom A y a) + ( ϕ : (z : A) → hom A z a → hom A z b) + : hom A x b + := + \ t → + transformation-id-codomain-square A is-pre-∞-category-A a b x y f v ϕ t t + +-- One half of transformation-id-codomain-square. +#def witness-comp-transformation-id-codomain-square + ( A : U) + ( is-pre-∞-category-A : is-pre-∞-category A) + ( a b x y : A) + ( f : hom A x y) + ( v : hom A y a) + ( ϕ : (z : A) → hom A z a → hom A z b) + : hom2 A x y b f (ϕ y v) + ( diagonal-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + := + \ (t , s) → + transformation-id-codomain-square A is-pre-∞-category-A a b x y f v ϕ t s + +-- The associated coherence. +#def coherence-witness-comp-transformation-id-codomain-square + ( A : U) + ( is-pre-∞-category-A : is-pre-∞-category A) + ( a b x y : A) + ( f : hom A x y) + ( v : hom A y a) + ( ϕ : (z : A) → hom A z a → hom A z b) + : ( comp-is-pre-∞-category A is-pre-∞-category-A x y b f (ϕ y v)) + = ( diagonal-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + := + uniqueness-comp-is-pre-∞-category A is-pre-∞-category-A x y b f (ϕ y v) + ( diagonal-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + ( witness-comp-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + +-- The other half of transformation-id-codomain-square. +#def witness-id-transformation-id-codomain-square + ( A : U) + ( is-pre-∞-category-A : is-pre-∞-category A) + ( a b x y : A) + ( f : hom A x y) + ( v : hom A y a) + ( ϕ : (z : A) → hom A z a → hom A z b) + : hom2 A x b b + ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x y a f v)) + ( id-hom A b) + ( diagonal-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + := + \ (t , s) → + transformation-id-codomain-square A is-pre-∞-category-A a b x y f v ϕ s t + +-- The associated coherence. +#def coherence-witness-id-transformation-id-codomain-square + ( A : U) + ( is-pre-∞-category-A : is-pre-∞-category A) + ( a b x y : A) + ( f : hom A x y) + ( v : hom A y a) + ( ϕ : (z : A) → hom A z a → hom A z b) + : ( comp-is-pre-∞-category A is-pre-∞-category-A x b b + ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x y a f v)) + ( id-hom A b)) + = ( diagonal-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + := + uniqueness-comp-is-pre-∞-category A is-pre-∞-category-A x b b + ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x y a f v)) + ( id-hom A b) + ( diagonal-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + ( witness-id-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + +#def simplified-coherence-witness-id-transformation-id-codomain-square + ( A : U) + ( is-pre-∞-category-A : is-pre-∞-category A) + ( a b x y : A) + ( f : hom A x y) + ( v : hom A y a) + ( ϕ : (z : A) → hom A z a → hom A z b) + : ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x y a f v)) + = ( diagonal-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + := + zag-zig-concat (hom A x b) + ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x y a f v)) + ( comp-is-pre-∞-category A is-pre-∞-category-A x b b + ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x y a f v)) + ( id-hom A b)) + ( diagonal-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + ( comp-id-is-pre-∞-category A is-pre-∞-category-A x b + ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x y a f v))) + ( coherence-witness-id-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + +#def naturality-contravariant-fiberwise-representable-transformation** + ( A : U) + ( is-pre-∞-category-A : is-pre-∞-category A) + ( a b x y : A) + ( f : hom A x y) + ( v : hom A y a) + ( ϕ : (z : A) → hom A z a → hom A z b) + : ( comp-is-pre-∞-category A is-pre-∞-category-A x y b f (ϕ y v)) + = ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x y a f v)) + := + zig-zag-concat (hom A x b) + ( comp-is-pre-∞-category A is-pre-∞-category-A x y b f (ϕ y v)) + ( diagonal-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x y a f v)) + ( coherence-witness-comp-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) + ( simplified-coherence-witness-id-transformation-id-codomain-square + A is-pre-∞-category-A a b x y f v ϕ) ``` For any pre-∞-category $A$ terms $a b : A$, the contravariant Yoneda lemma @@ -82,12 +239,7 @@ The inverse map only exists for pre-∞-categories. ( is-pre-∞-category-A : is-pre-∞-category A) ( a b : A) : hom A a b → ((z : A) → hom A z a → hom A z b) - := - \ v z f → - contravariant-transport A z a f - ( \ z → hom A z b) - ( is-contravariant-representable-is-pre-∞-category A is-pre-∞-category-A b) - ( v) + := \ v z f → comp-is-pre-∞-category A is-pre-∞-category-A z a b f v ``` It remains to show that the Yoneda maps are inverses. One retraction is @@ -101,10 +253,7 @@ straightforward: ( v : hom A a b) : contra-evid* A a b (contra-yon* A is-pre-∞-category-A a b v) = v := - id-arr-contravariant-transport A a - ( \ z → hom A z b) - ( is-contravariant-representable-is-pre-∞-category A is-pre-∞-category-A b) - ( v) + id-comp-is-pre-∞-category A is-pre-∞-category-A a b v ``` The other composite carries $ϕ$ to an a priori distinct natural transformation. @@ -136,8 +285,8 @@ The composite `#!rzk contra-yon-evid` of `#!rzk ϕ` equals `#!rzk ϕ` at all ( ( contra-evid* A a b) ϕ)) x f) ( ϕ x (comp-is-pre-∞-category A is-pre-∞-category-A x a a f (id-hom A a))) ( ϕ x f) - ( naturality-contravariant-fiberwise-representable-transformation* - A is-pre-∞-category-A a b x a (id-hom A a) f ϕ) + ( naturality-contravariant-fiberwise-representable-transformation** + A is-pre-∞-category-A a b x a f (id-hom A a) ϕ) ( ap ( hom A x a) ( hom A x b) @@ -243,11 +392,9 @@ Naturality in $b$ is not automatic but can be proven easily: ( \ α z g → ψ z (α z g)) ( contra-yon* A is-pre-∞-category-A a b)) u x f := - naturality-contravariant-fiberwise-transformation - A x a f (\ z → hom A z b) (\ z → hom A z b') - ( is-contravariant-representable-is-pre-∞-category A is-pre-∞-category-A b) - ( is-contravariant-representable-is-pre-∞-category A is-pre-∞-category-A b') - ψ u + naturality-contravariant-fiberwise-representable-transformation** + A is-pre-∞-category-A b b' x a f u ψ + #def is-natural-in-family-contra-yon-once-pointwise* uses (funext) ( A : U)