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CW complexes, cellular homology + a lot more (#1111)
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{-# OPTIONS --safe #-} | ||
module Cubical.Algebra.ChainComplex where | ||
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open import Cubical.Algebra.ChainComplex.Base public | ||
open import Cubical.Algebra.ChainComplex.Homology public | ||
open import Cubical.Algebra.ChainComplex.Finite public |
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{-# OPTIONS --safe --lossy-unification #-} | ||
module Cubical.Algebra.ChainComplex.Base where | ||
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open import Cubical.Foundations.Prelude | ||
open import Cubical.Foundations.Function | ||
open import Cubical.Foundations.Equiv | ||
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open import Cubical.Data.Sigma | ||
open import Cubical.Data.Nat | ||
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open import Cubical.Algebra.Group | ||
open import Cubical.Algebra.Group.MorphismProperties | ||
open import Cubical.Algebra.AbGroup | ||
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private | ||
variable | ||
ℓ ℓ' ℓ'' : Level | ||
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record ChainComplex (ℓ : Level) : Type (ℓ-suc ℓ) where | ||
field | ||
chain : (i : ℕ) → AbGroup ℓ | ||
bdry : (i : ℕ) → AbGroupHom (chain (suc i)) (chain i) | ||
bdry²=0 : (i : ℕ) → compGroupHom (bdry (suc i)) (bdry i) ≡ trivGroupHom | ||
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record ChainComplexMap {ℓ ℓ' : Level} | ||
(A : ChainComplex ℓ) (B : ChainComplex ℓ') : Type (ℓ-max ℓ ℓ') where | ||
open ChainComplex | ||
field | ||
chainmap : (i : ℕ) → AbGroupHom (chain A i) (chain B i) | ||
bdrycomm : (i : ℕ) | ||
→ compGroupHom (chainmap (suc i)) (bdry B i) ≡ compGroupHom (bdry A i) (chainmap i) | ||
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record ChainHomotopy {ℓ : Level} {A : ChainComplex ℓ} {B : ChainComplex ℓ'} | ||
(f g : ChainComplexMap A B) : Type (ℓ-max ℓ' ℓ) where | ||
open ChainComplex | ||
open ChainComplexMap | ||
field | ||
htpy : (i : ℕ) → AbGroupHom (chain A i) (chain B (suc i)) | ||
bdryhtpy : (i : ℕ) | ||
→ subtrGroupHom (chain A (suc i)) (chain B (suc i)) | ||
(chainmap f (suc i)) (chainmap g (suc i)) | ||
≡ addGroupHom (chain A (suc i)) (chain B (suc i)) | ||
(compGroupHom (htpy (suc i)) (bdry B (suc i))) | ||
(compGroupHom (bdry A i) (htpy i)) | ||
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record CoChainComplex (ℓ : Level) : Type (ℓ-suc ℓ) where | ||
field | ||
cochain : (i : ℕ) → AbGroup ℓ | ||
cobdry : (i : ℕ) → AbGroupHom (cochain i) (cochain (suc i)) | ||
cobdry²=0 : (i : ℕ) → compGroupHom (cobdry i) (cobdry (suc i)) | ||
≡ trivGroupHom | ||
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open ChainComplexMap | ||
ChainComplexMap≡ : {A : ChainComplex ℓ} {B : ChainComplex ℓ'} | ||
{f g : ChainComplexMap A B} | ||
→ ((i : ℕ) → chainmap f i ≡ chainmap g i) | ||
→ f ≡ g | ||
chainmap (ChainComplexMap≡ p i) n = p n i | ||
bdrycomm (ChainComplexMap≡ {A = A} {B = B} {f = f} {g = g} p i) n = | ||
isProp→PathP {B = λ i → compGroupHom (p (suc n) i) (ChainComplex.bdry B n) | ||
≡ compGroupHom (ChainComplex.bdry A n) (p n i)} | ||
(λ i → isSetGroupHom _ _) | ||
(bdrycomm f n) (bdrycomm g n) i | ||
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compChainMap : {A : ChainComplex ℓ} {B : ChainComplex ℓ'} {C : ChainComplex ℓ''} | ||
→ (f : ChainComplexMap A B) (g : ChainComplexMap B C) | ||
→ ChainComplexMap A C | ||
compChainMap {A = A} {B} {C} ϕ' ψ' = main | ||
where | ||
ϕ = chainmap ϕ' | ||
commϕ = bdrycomm ϕ' | ||
ψ = chainmap ψ' | ||
commψ = bdrycomm ψ' | ||
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main : ChainComplexMap A C | ||
chainmap main n = compGroupHom (ϕ n) (ψ n) | ||
bdrycomm main n = | ||
Σ≡Prop (λ _ → isPropIsGroupHom _ _) | ||
(funExt λ x | ||
→ (funExt⁻ (cong fst (commψ n)) (ϕ (suc n) .fst x)) | ||
∙ cong (fst (ψ n)) (funExt⁻ (cong fst (commϕ n)) x)) | ||
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isChainEquiv : {A : ChainComplex ℓ} {B : ChainComplex ℓ'} | ||
→ ChainComplexMap A B → Type (ℓ-max ℓ ℓ') | ||
isChainEquiv f = ((n : ℕ) → isEquiv (chainmap f n .fst)) | ||
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_≃Chain_ : (A : ChainComplex ℓ) (B : ChainComplex ℓ') → Type (ℓ-max ℓ ℓ') | ||
A ≃Chain B = Σ[ f ∈ ChainComplexMap A B ] (isChainEquiv f) | ||
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idChainMap : (A : ChainComplex ℓ) → ChainComplexMap A A | ||
chainmap (idChainMap A) _ = idGroupHom | ||
bdrycomm (idChainMap A) _ = | ||
Σ≡Prop (λ _ → isPropIsGroupHom _ _) refl | ||
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invChainMap : {A : ChainComplex ℓ} {B : ChainComplex ℓ'} | ||
→ (A ≃Chain B) → ChainComplexMap B A | ||
chainmap (invChainMap (ϕ , eq)) n = | ||
GroupEquiv→GroupHom (invGroupEquiv ((chainmap ϕ n .fst , eq n) , snd (chainmap ϕ n))) | ||
bdrycomm (invChainMap {B = B} (ϕ' , eq)) n = | ||
Σ≡Prop (λ _ → isPropIsGroupHom _ _) | ||
(funExt λ x | ||
→ sym (retEq (_ , eq n ) _) | ||
∙∙ cong (invEq (_ , eq n )) | ||
(sym (funExt⁻ (cong fst (ϕcomm n)) (invEq (_ , eq (suc n)) x))) | ||
∙∙ cong (invEq (ϕ n .fst , eq n ) ∘ fst (ChainComplex.bdry B n)) | ||
(secEq (_ , eq (suc n)) x)) | ||
where | ||
ϕ = chainmap ϕ' | ||
ϕcomm = bdrycomm ϕ' | ||
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invChainEquiv : {A : ChainComplex ℓ} {B : ChainComplex ℓ'} | ||
→ A ≃Chain B → B ≃Chain A | ||
fst (invChainEquiv e) = invChainMap e | ||
snd (invChainEquiv e) n = snd (invEquiv (chainmap (fst e) n .fst , snd e n)) |
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{-# OPTIONS --safe --lossy-unification #-} | ||
module Cubical.Algebra.ChainComplex.Finite where | ||
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{- When dealing with chain maps and chain homotopies constructively, | ||
it is often the case the case that one only is able to obtain a finite | ||
approximation rather than the full thing. This file contains | ||
definitions of | ||
(1) finite chain maps, | ||
(2) finite chain homotopies | ||
(3) finite chain equivalences | ||
and proof their induced behaviour on homology | ||
-} | ||
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open import Cubical.Foundations.Prelude | ||
open import Cubical.Foundations.Function | ||
open import Cubical.Foundations.Equiv | ||
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open import Cubical.Data.Sigma | ||
open import Cubical.Data.Nat | ||
open import Cubical.Data.Fin.Inductive.Base | ||
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open import Cubical.Algebra.ChainComplex.Base | ||
open import Cubical.Algebra.Group.MorphismProperties | ||
open import Cubical.Algebra.AbGroup | ||
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private | ||
variable | ||
ℓ ℓ' ℓ'' : Level | ||
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module _ where | ||
record finChainComplexMap {ℓ ℓ' : Level} (m : ℕ) | ||
(A : ChainComplex ℓ) (B : ChainComplex ℓ') : Type (ℓ-max ℓ ℓ') where | ||
open ChainComplex | ||
field | ||
fchainmap : (i : Fin (suc m)) | ||
→ AbGroupHom (chain A (fst i)) (chain B (fst i)) | ||
fbdrycomm : (i : Fin m) | ||
→ compGroupHom (fchainmap (fsuc i)) (bdry B (fst i)) | ||
≡ compGroupHom (bdry A (fst i)) (fchainmap (injectSuc i)) | ||
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record finChainHomotopy {ℓ : Level} (m : ℕ) | ||
{A : ChainComplex ℓ} {B : ChainComplex ℓ'} | ||
(f g : finChainComplexMap m A B) : Type (ℓ-max ℓ' ℓ) where | ||
open ChainComplex | ||
open finChainComplexMap | ||
field | ||
fhtpy : (i : Fin (suc m)) | ||
→ AbGroupHom (chain A (fst i)) (chain B (suc (fst i))) | ||
fbdryhtpy : (i : Fin m) | ||
→ subtrGroupHom (chain A (suc (fst i))) (chain B (suc (fst i))) | ||
(fchainmap f (fsuc i)) (fchainmap g (fsuc i)) | ||
≡ addGroupHom (chain A (suc (fst i))) (chain B (suc (fst i))) | ||
(compGroupHom (fhtpy (fsuc i)) (bdry B (suc (fst i)))) | ||
(compGroupHom (bdry A (fst i)) (fhtpy (injectSuc i))) | ||
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open finChainComplexMap | ||
finChainComplexMap≡ : | ||
{A : ChainComplex ℓ} {B : ChainComplex ℓ'} {m : ℕ} | ||
{f g : finChainComplexMap m A B} | ||
→ ((i : Fin (suc m)) → fchainmap f i ≡ fchainmap g i) | ||
→ f ≡ g | ||
fchainmap (finChainComplexMap≡ p i) n = p n i | ||
fbdrycomm (finChainComplexMap≡ {A = A} {B = B} {f = f} {g = g} p i) n = | ||
isProp→PathP {B = λ i | ||
→ compGroupHom (p (fsuc n) i) (ChainComplex.bdry B (fst n)) | ||
≡ compGroupHom (ChainComplex.bdry A (fst n)) (p (injectSuc n) i)} | ||
(λ i → isSetGroupHom _ _) | ||
(fbdrycomm f n) (fbdrycomm g n) i | ||
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compFinChainMap : | ||
{A : ChainComplex ℓ} {B : ChainComplex ℓ'} {C : ChainComplex ℓ''} {m : ℕ} | ||
→ (f : finChainComplexMap m A B) (g : finChainComplexMap m B C) | ||
→ finChainComplexMap m A C | ||
compFinChainMap {A = A} {B} {C} {m = m} ϕ' ψ' = main | ||
where | ||
ϕ = fchainmap ϕ' | ||
commϕ = fbdrycomm ϕ' | ||
ψ = fchainmap ψ' | ||
commψ = fbdrycomm ψ' | ||
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main : finChainComplexMap m A C | ||
fchainmap main n = compGroupHom (ϕ n) (ψ n) | ||
fbdrycomm main n = | ||
Σ≡Prop (λ _ → isPropIsGroupHom _ _) | ||
(funExt λ x | ||
→ (funExt⁻ (cong fst (commψ n)) (ϕ (fsuc n) .fst x)) | ||
∙ cong (fst (ψ (injectSuc n))) (funExt⁻ (cong fst (commϕ n)) x)) | ||
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isFinChainEquiv : {A : ChainComplex ℓ} {B : ChainComplex ℓ'} {m : ℕ} | ||
→ finChainComplexMap m A B → Type (ℓ-max ℓ ℓ') | ||
isFinChainEquiv {m = m} f = ((n : Fin (suc m)) → isEquiv (fchainmap f n .fst)) | ||
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_≃⟨_⟩Chain_ : (A : ChainComplex ℓ) (m : ℕ) (B : ChainComplex ℓ') | ||
→ Type (ℓ-max ℓ ℓ') | ||
A ≃⟨ m ⟩Chain B = Σ[ f ∈ finChainComplexMap m A B ] (isFinChainEquiv f) | ||
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idFinChainMap : (m : ℕ) (A : ChainComplex ℓ) → finChainComplexMap m A A | ||
fchainmap (idFinChainMap m A) _ = idGroupHom | ||
fbdrycomm (idFinChainMap m A) _ = | ||
Σ≡Prop (λ _ → isPropIsGroupHom _ _) refl | ||
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invFinChainMap : {A : ChainComplex ℓ} {B : ChainComplex ℓ'} {m : ℕ} | ||
→ (A ≃⟨ m ⟩Chain B) → finChainComplexMap m B A | ||
fchainmap (invFinChainMap {m = m} (ϕ , eq)) n = | ||
GroupEquiv→GroupHom | ||
(invGroupEquiv ((fchainmap ϕ n .fst , eq n) , snd (fchainmap ϕ n))) | ||
fbdrycomm (invFinChainMap {B = B} {m = m} (ϕ' , eq)) n = | ||
Σ≡Prop (λ _ → isPropIsGroupHom _ _) | ||
(funExt λ x | ||
→ sym (retEq (_ , eq (injectSuc n) ) _) | ||
∙∙ cong (invEq (_ , eq (injectSuc n) )) | ||
(sym (funExt⁻ (cong fst (ϕcomm n)) (invEq (_ , eq (fsuc n)) x))) | ||
∙∙ cong (invEq (ϕ (injectSuc n) .fst , eq (injectSuc n) ) | ||
∘ fst (ChainComplex.bdry B (fst n))) | ||
(secEq (_ , eq (fsuc n)) x)) | ||
where | ||
ϕ = fchainmap ϕ' | ||
ϕcomm = fbdrycomm ϕ' | ||
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invFinChainEquiv : {A : ChainComplex ℓ} {B : ChainComplex ℓ'} {m : ℕ} | ||
→ A ≃⟨ m ⟩Chain B → B ≃⟨ m ⟩Chain A | ||
fst (invFinChainEquiv e) = invFinChainMap e | ||
snd (invFinChainEquiv e) n = snd (invEquiv (fchainmap (fst e) n .fst , snd e n)) |
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