concise course in algebraic topology

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Michael Zhang 2024-05-23 09:38:54 -05:00
parent 71b5471d14
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@ -738,31 +738,55 @@ open axiom2∙10∙3
### Theorem 2.11.1
```
-- theorem2∙11∙1 : {A B : Set}
-- → (eqv @ (f , f-eqv) : A ≃ B)
-- → (a a' : A)
-- → (a ≡ a') ≃ (f a ≡ f a')
-- theorem2∙11∙1 (f , f-eqv) a a' =
-- let
-- open ≡-Reasoning
-- mkQinv g α β = isequiv-to-qinv f-eqv
-- inv : (f a ≡ f a') → a ≡ a'
-- inv p = (sym (β a)) ∙ (ap g p) ∙ (β a')
-- backward : (p : f a ≡ f a') → (ap f ∘ inv) p ≡ id p
-- backward q = begin
-- ap f ((sym (β a)) ∙ (ap g q) ∙ (β a')) ≡⟨ lemma2∙2∙2.i (sym (β a)) (ap g q ∙ β a') ⟩
-- ap f (sym (β a)) ∙ ap f ((ap g q) ∙ (β a')) ≡⟨ {! !} ⟩
-- ap f (sym (β a)) ∙ ap f ((ap g q) ∙ (β a')) ≡⟨ {! !} ⟩
-- id q ∎
-- forward : (p : a ≡ a') → (inv ∘ ap f) p ≡ id p
-- forward p = begin
-- (sym (β a)) ∙ (ap g (ap f p)) ∙ (β a') ≡⟨ ap (λ p → (sym (β a)) ∙ p ∙ (β a')) (lemma2∙2∙2.iii f g p) ⟩
-- (sym (β a)) ∙ (ap (g ∘ f) p) ∙ (β a') ≡⟨ {! !} ⟩
-- (sym (β a)) ∙ (ap id p) ∙ (β a') ≡⟨ {! !} ⟩
-- id p ∎
-- eqv = mkQinv inv backward forward
-- in
-- ap f , qinv-to-isequiv eqv
theorem2∙11∙1 : {A B : Set}
→ (eqv @ (f , f-eqv) : A ≃ B)
→ (a a' : A)
→ (a ≡ a') ≃ (f a ≡ f a')
theorem2∙11∙1 (f , f-eqv) a a' =
let
open ≡-Reasoning
mkQinv g α β = isequiv-to-qinv f-eqv
inv : (f a ≡ f a') → a ≡ a'
inv p = (sym (β a)) ∙ (ap g p) ∙ (β a')
backward : (p : f a ≡ f a') → (ap f ∘ inv) p ≡ id p
backward q = begin
ap f ((sym (β a)) ∙ (ap g q) ∙ (β a')) ≡⟨ lemma2∙2∙2.i (sym (β a)) (ap g q ∙ β a') ⟩
ap f (sym (β a)) ∙ ap f ((ap g q) ∙ (β a')) ≡⟨ {! !} ⟩
ap f (sym (β a)) ∙ ap f ((ap g q) ∙ (β a')) ≡⟨ {! !} ⟩
id q ∎
forward : (p : a ≡ a') → (inv ∘ ap f) p ≡ id p
forward p = begin
(sym (β a)) ∙ (ap g (ap f p)) ∙ (β a') ≡⟨ ap (λ p → (sym (β a)) ∙ p ∙ (β a')) (lemma2∙2∙2.iii f g p) ⟩
(sym (β a)) ∙ (ap (g ∘ f) p) ∙ (β a') ≡⟨ {! !} ⟩
-- (sym (β a)) ∙ (ap id p) ∙ (β a') ≡⟨ {! !} ⟩
id p ∎
eqv = mkQinv inv backward forward
in
ap f , qinv-to-isequiv eqv
```
### Theorem 2.11.2
```
-- module theorem2∙11∙2 where
-- i : {A : Set} {a x1 x2 : A}
-- → (p : x1 ≡ x2)
-- → (q : a ≡ x1)
-- → transport (λ y → a ≡ y) p q ≡ q ∙ p
-- i {A} {a} {x1} {x2} p q =
-- J (λ x3 x4 p1 → (q1 : a ≡ x3) → transport (λ y → a ≡ y) p1 q1 ≡ q1 ∙ p1)
-- (λ x3 q1 → J (λ x5 x6 q2 → transport (λ y → a ≡ y) refl q1 ≡ q1 ∙ refl) (λ x4 → {! refl !}) a x3 q1)
-- x1 x2 p q
```
### Theorem 2.11.3
```
theorem2∙11∙3 : {A B : Set} → {f g : A → B} → {a a' : A}
→ (p : a ≡ a')
→ (q : f a ≡ g a)
→ transport (λ x → f x ≡ g x) p q ≡ sym (ap f p) ∙ q ∙ (ap g p)
theorem2∙11∙3 p q = {! !}
```
## 2.12 Coproducts

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@ -3,6 +3,7 @@ module HottBook.Chapter6 where
open import HottBook.Chapter1
open import HottBook.Chapter2
open import HottBook.Chapter2Lemma221
```
# 6 Higher inductive types
@ -10,12 +11,14 @@ open import HottBook.Chapter2
### Definition 6.2.2 (Dependent paths)
```
dep-path : {A : Set}
definition6∙2∙2 : {A : Set}
→ (P : A → Set)
→ {x y : A}
→ (p : x ≡ y)
→ (u : P x) → (v : P y) → Set
dep-path P p u v = transport P p u ≡ v
definition6∙2∙2 P p u v = transport P p u ≡ v
syntax definition6∙2∙2 P p u v = u ≡[ P , p ] v
```
Circle definition
@ -27,28 +30,34 @@ postulate
loop : base ≡ base
S¹-elim : (P : S¹ → Set)
→ (p-base : P base)
→ (p-loop : dep-path P loop p-base p-base)
→ (p-loop : p-base ≡[ P , loop ] p-base)
→ (x : S¹) → P x
```
### Lemma 6.2.5
```
lemma6∙2∙5 : {A : Set}
→ (a : A)
→ (p : a ≡ a)
→ S¹ → A
lemma6∙2∙5 : {A : Set} → (a : A) → (p : a ≡ a) → S¹ → A
lemma6∙2∙5 {A} a p circ = S¹-elim P p-base p-loop circ
where
P : S¹ → Set
P _ = A
p-base : P base
p-base = a
p-loop : transport P loop a ≡ a
p-loop =
let wtf = lemma2∙3∙8 (λ x → {! !}) loop in
{! !}
p-loop : a ≡[ P , loop ] a
p-loop = transportconst A loop a ∙ p
```
### Lemma 6.2.8
```
lemma6∙2∙8 : {A : Set} {f g : S¹ → A}
→ (p : f base ≡ g base)
→ (q : (ap f loop) ≡[ (λ x → x ≡ x) , p ] (ap g loop))
→ (x : S¹) → f x ≡ g x
lemma6∙2∙8 {A} {f} {g} p q = S¹-elim (λ x → f x ≡ g x) p {! !}
```
## 6.3 The interval