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Base change, sliced adjoints (#1120)
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{-# OPTIONS --safe #-} | ||
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module Cubical.Categories.Constructions.Slice.Functor where | ||
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open import Cubical.Foundations.Prelude | ||
open import Cubical.Foundations.Function | ||
open import Cubical.Foundations.Isomorphism | ||
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open import Cubical.Categories.Category | ||
open import Cubical.Categories.Category.Properties | ||
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open import Cubical.Categories.Constructions.Slice.Base | ||
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open import Cubical.Categories.Limits.Pullback | ||
open import Cubical.Categories.Functor | ||
open import Cubical.Categories.NaturalTransformation | ||
open import Cubical.Categories.Adjoint | ||
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open import Cubical.Tactics.FunctorSolver.Reflection | ||
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open Category hiding (_∘_) | ||
open Functor | ||
open NatTrans | ||
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private | ||
variable | ||
ℓ ℓ' : Level | ||
C D : Category ℓ ℓ' | ||
c d : C .ob | ||
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infix 39 _F/_ | ||
infix 40 ∑_ | ||
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_F/_ : ∀ (F : Functor C D) c → Functor (SliceCat C c) (SliceCat D (F ⟅ c ⟆)) | ||
F-ob (F F/ c) = sliceob ∘ F ⟪_⟫ ∘ S-arr | ||
F-hom (F F/ c) h = slicehom _ | ||
$ sym ( F-seq F _ _) ∙ cong (F ⟪_⟫) (S-comm h) | ||
F-id (F F/ c) = SliceHom-≡-intro' _ _ $ F-id F | ||
F-seq (F F/ c) _ _ = SliceHom-≡-intro' _ _ $ F-seq F _ _ | ||
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∑_ : ∀ {c d} f → Functor (SliceCat C c) (SliceCat C d) | ||
F-ob (∑_ {C = C} f) (sliceob x) = sliceob (x ⋆⟨ C ⟩ f) | ||
F-hom (∑_ {C = C} f) (slicehom h p) = slicehom _ $ | ||
sym (C .⋆Assoc _ _ _) ∙ cong (comp' C f) p | ||
F-id (∑ f) = SliceHom-≡-intro' _ _ refl | ||
F-seq (∑ f) _ _ = SliceHom-≡-intro' _ _ refl | ||
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module _ (Pbs : Pullbacks C) where | ||
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open Category C using () renaming (_⋆_ to _⋆ᶜ_) | ||
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module BaseChange {c d} (𝑓 : C [ c , d ]) where | ||
infix 40 _* | ||
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module _ {x@(sliceob arr) : SliceOb C d} where | ||
open Pullback (Pbs (cospan _ _ _ 𝑓 arr)) public | ||
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module _ {x} {y} ((slicehom h h-comm) : SliceCat C d [ y , x ]) where | ||
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pbU = univProp (pbPr₁ {x = y}) (pbPr₂ ⋆ᶜ h) | ||
(pbCommutes {x = y} ∙∙ cong (pbPr₂ ⋆ᶜ_) (sym (h-comm)) ∙∙ sym (C .⋆Assoc _ _ _)) | ||
.fst .snd | ||
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_* : Functor (SliceCat C d) (SliceCat C c) | ||
F-ob _* x = sliceob (pbPr₁ {x = x}) | ||
F-hom _* f = slicehom _ (sym (fst (pbU f))) | ||
F-id _* = SliceHom-≡-intro' _ _ $ pullbackArrowUnique (sym (C .⋆IdL _)) (C .⋆IdR _ ∙ sym (C .⋆IdL _)) | ||
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F-seq _* _ _ = | ||
let (u₁ , v₁) = pbU _ ; (u₂ , v₂) = pbU _ | ||
in SliceHom-≡-intro' _ _ $ pullbackArrowUnique | ||
(u₂ ∙∙ cong (C ⋆ _) u₁ ∙∙ sym (C .⋆Assoc _ _ _)) | ||
(sym (C .⋆Assoc _ _ _) ∙∙ cong (comp' C _) v₂ ∙∙ AssocCong₂⋆R C v₁) | ||
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open BaseChange using (_*) | ||
open NaturalBijection renaming (_⊣_ to _⊣₂_) | ||
open Iso | ||
open _⊣₂_ | ||
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module _ (𝑓 : C [ c , d ]) where | ||
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open BaseChange 𝑓 hiding (_*) | ||
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∑𝑓⊣𝑓* : ∑ 𝑓 ⊣₂ 𝑓 * | ||
fun (adjIso ∑𝑓⊣𝑓*) (slicehom h o) = | ||
let ((_ , (p , _)) , _) = univProp _ _ (sym o) | ||
in slicehom _ (sym p) | ||
inv (adjIso ∑𝑓⊣𝑓*) (slicehom h o) = slicehom _ $ | ||
AssocCong₂⋆R C (sym (pbCommutes)) ∙ cong (_⋆ᶜ 𝑓) o | ||
rightInv (adjIso ∑𝑓⊣𝑓*) (slicehom h o) = | ||
SliceHom-≡-intro' _ _ (pullbackArrowUnique (sym o) refl) | ||
leftInv (adjIso ∑𝑓⊣𝑓*) (slicehom h o) = | ||
let ((_ , (_ , q)) , _) = univProp _ _ _ | ||
in SliceHom-≡-intro' _ _ (sym q) | ||
adjNatInD ∑𝑓⊣𝑓* f k = SliceHom-≡-intro' _ _ $ | ||
let ((h' , (v' , u')) , _) = univProp _ _ _ | ||
((_ , (v'' , u'')) , _) = univProp _ _ _ | ||
in pullbackArrowUnique (v' ∙∙ cong (h' ⋆ᶜ_) v'' ∙∙ sym (C .⋆Assoc _ _ _)) | ||
(cong (_⋆ᶜ _) u' ∙ AssocCong₂⋆R C u'') | ||
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adjNatInC ∑𝑓⊣𝑓* g h = SliceHom-≡-intro' _ _ $ C .⋆Assoc _ _ _ | ||
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open UnitCounit | ||
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module SlicedAdjoint {L : Functor C D} {R} (L⊣R : L ⊣ R) where | ||
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open Category D using () renaming (_⋆_ to _⋆ᵈ_) | ||
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open _⊣_ L⊣R | ||
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module _ {c} {d} where | ||
module aI = Iso (adjIso (adj→adj' _ _ L⊣R) {c} {d}) | ||
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module Left (b : D .ob) where | ||
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⊣F/ : Functor (SliceCat C (R ⟅ b ⟆)) (SliceCat D b) | ||
⊣F/ = ∑ (ε ⟦ b ⟧) ∘F L F/ (R ⟅ b ⟆) | ||
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L/b⊣R/b : ⊣F/ ⊣₂ (R F/ b) | ||
fun (adjIso L/b⊣R/b) (slicehom _ p) = slicehom _ $ | ||
C .⋆Assoc _ _ _ | ||
∙∙ cong (_ ⋆ᶜ_) (sym (F-seq R _ _) ∙∙ cong (R ⟪_⟫) p ∙∙ F-seq R _ _) | ||
∙∙ AssocCong₂⋆L C (sym (N-hom η _)) | ||
∙∙ cong (_ ⋆ᶜ_) (Δ₂ _) | ||
∙∙ C .⋆IdR _ | ||
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inv (adjIso L/b⊣R/b) (slicehom _ p) = | ||
slicehom _ $ AssocCong₂⋆R D (sym (N-hom ε _)) | ||
∙ cong (_⋆ᵈ _) (sym (F-seq L _ _) ∙ cong (L ⟪_⟫) p) | ||
rightInv (adjIso L/b⊣R/b) _ = SliceHom-≡-intro' _ _ $ aI.rightInv _ | ||
leftInv (adjIso L/b⊣R/b) _ = SliceHom-≡-intro' _ _ $ aI.leftInv _ | ||
adjNatInD L/b⊣R/b _ _ = SliceHom-≡-intro' _ _ $ | ||
cong (_ ⋆ᶜ_) (F-seq R _ _) ∙ sym (C .⋆Assoc _ _ _) | ||
adjNatInC L/b⊣R/b _ _ = SliceHom-≡-intro' _ _ $ | ||
cong (_⋆ᵈ _) (F-seq L _ _) ∙ (D .⋆Assoc _ _ _) | ||
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module Right (b : C .ob) where | ||
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F/⊣ : Functor (SliceCat D (L ⟅ b ⟆)) (SliceCat C b) | ||
F/⊣ = (η ⟦ b ⟧) * ∘F R F/ (L ⟅ b ⟆) | ||
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open BaseChange (η ⟦ b ⟧) hiding (_*) | ||
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L/b⊣R/b : L F/ b ⊣₂ F/⊣ | ||
fun (adjIso L/b⊣R/b) (slicehom f s) = slicehom _ $ | ||
sym $ univProp _ _ (N-hom η _ ∙∙ | ||
cong (_ ⋆ᶜ_) (cong (R ⟪_⟫) (sym s) ∙ F-seq R _ _) | ||
∙∙ sym (C .⋆Assoc _ _ _)) .fst .snd .fst | ||
inv (adjIso L/b⊣R/b) (slicehom f s) = slicehom _ | ||
(D .⋆Assoc _ _ _ | ||
∙∙ congS (_⋆ᵈ (ε ⟦ _ ⟧ ⋆⟨ D ⟩ _)) (F-seq L _ _) | ||
∙∙ D .⋆Assoc _ _ _ ∙ cong (L ⟪ f ⟫ ⋆ᵈ_) | ||
(cong (L ⟪ pbPr₂ ⟫ ⋆ᵈ_) (sym (N-hom ε _)) | ||
∙∙ sym (D .⋆Assoc _ _ _) | ||
∙∙ cong (_⋆ᵈ ε ⟦ F-ob L b ⟧) | ||
(preserveCommF L $ sym pbCommutes) | ||
∙∙ D .⋆Assoc _ _ _ | ||
∙∙ cong (L ⟪ pbPr₁ ⟫ ⋆ᵈ_) (Δ₁ b) | ||
∙ D .⋆IdR _) | ||
∙∙ sym (F-seq L _ _) | ||
∙∙ cong (L ⟪_⟫) s) | ||
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rightInv (adjIso L/b⊣R/b) h = SliceHom-≡-intro' _ _ $ | ||
let p₂ : ∀ {x} → η ⟦ _ ⟧ ⋆ᶜ R ⟪ L ⟪ x ⟫ ⋆⟨ D ⟩ ε ⟦ _ ⟧ ⟫ ≡ x | ||
p₂ = cong (_ ⋆ᶜ_) (F-seq R _ _) ∙ | ||
AssocCong₂⋆L C (sym (N-hom η _)) | ||
∙∙ cong (_ ⋆ᶜ_) (Δ₂ _) ∙∙ C .⋆IdR _ | ||
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in pullbackArrowUnique (sym (S-comm h)) p₂ | ||
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leftInv (adjIso L/b⊣R/b) _ = SliceHom-≡-intro' _ _ $ | ||
cong ((_⋆ᵈ _) ∘ L ⟪_⟫) (sym (snd (snd (fst (univProp _ _ _))))) | ||
∙ aI.leftInv _ | ||
adjNatInD L/b⊣R/b _ _ = SliceHom-≡-intro' _ _ $ | ||
let (h , (u , v)) = univProp _ _ _ .fst | ||
(u' , v') = pbU _ | ||
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in pullbackArrowUnique | ||
(u ∙∙ cong (h ⋆ᶜ_) u' ∙∙ sym (C .⋆Assoc h _ _)) | ||
(cong (_ ⋆ᶜ_) (F-seq R _ _) | ||
∙∙ sym (C .⋆Assoc _ _ _) ∙∙ | ||
(cong (_⋆ᶜ _) v ∙ AssocCong₂⋆R C v')) | ||
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adjNatInC L/b⊣R/b g h = let w = _ in SliceHom-≡-intro' _ _ $ | ||
cong (_⋆ᵈ _) (cong (L ⟪_⟫) (C .⋆Assoc _ _ w) ∙ F-seq L _ (_ ⋆ᶜ w)) | ||
∙ D .⋆Assoc _ _ _ | ||
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