continue on exact couples, simplify definition of bounded exact couple

This commit is contained in:
Floris van Doorn 2017-05-18 18:35:57 -04:00
parent cea1250ca6
commit 2c2fefd644
3 changed files with 258 additions and 97 deletions

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@ -119,7 +119,7 @@ definition graded_hom_mk_refl (d : I ≃ I)
(fn : Πi, M₁ i →lm M₂ (d i)) {i : I} (m : M₁ i) : graded_hom.mk d fn i m = fn i m :=
by reflexivity
definition graded_hom_mk_out'_left_inv (d : I ≃ I)
lemma graded_hom_mk_out'_left_inv (d : I ≃ I)
(fn : Πi, M₁ (d i) →lm M₂ i) {i : I} (m : M₁ (d i)) :
graded_hom.mk_out' d fn ↘ (left_inv d i) m = fn i m :=
begin
@ -129,6 +129,13 @@ begin
apply is_set.elim --we can also prove this in arbitrary types
end
lemma graded_hom_mk_out_right_inv (d : I ≃ I)
(fn : Πi, M₁ (d⁻¹ i) →lm M₂ i) {i : I} (m : M₁ (d⁻¹ i)) :
graded_hom.mk_out d fn ↘ (right_inv d i) m = fn i m :=
begin
rexact graded_hom_mk_out'_left_inv d⁻¹ᵉ fn m
end
definition graded_hom_eq_zero {f : M₁ →gm M₂} {i j k : I} {q : deg f i = j} {p : deg f i = k}
(m : M₁ i) (r : f ↘ q m = 0) : f ↘ p m = 0 :=
have f ↘ p m = transport M₂ (q⁻¹ ⬝ p) (f ↘ q m), begin induction p, induction q, reflexivity end,

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@ -2,7 +2,7 @@
-- Author: Floris van Doorn
import .graded ..homotopy.spectrum .product_group
import .graded ..homotopy.spectrum .product_group --types.int.order
open algebra is_trunc left_module is_equiv equiv eq function nat
@ -20,7 +20,75 @@ section
(H : is_exact_at A n) : is_exact (cc_to_fn A (S n)) (cc_to_fn A n) :=
is_exact.mk (cc_is_chain_complex A n) H
definition is_equiv_mul_right [constructor] {A : Group} (a : A) : is_equiv (λb, b * a) :=
adjointify _ (λb : A, b * a⁻¹) (λb, !inv_mul_cancel_right) (λb, !mul_inv_cancel_right)
definition right_action [constructor] {A : Group} (a : A) : A ≃ A :=
equiv.mk _ (is_equiv_mul_right a)
definition is_equiv_add_right [constructor] {A : AddGroup} (a : A) : is_equiv (λb, b + a) :=
adjointify _ (λb : A, b - a) (λb, !neg_add_cancel_right) (λb, !add_neg_cancel_right)
definition add_right_action [constructor] {A : AddGroup} (a : A) : A ≃ A :=
equiv.mk _ (is_equiv_add_right a)
section
variables {A B : Type} (f : A ≃ B) [ab_group A]
-- to group
definition group_equiv_mul_comm (b b' : B) : group_equiv_mul f b b' = group_equiv_mul f b' b :=
by rewrite [↑group_equiv_mul, mul.comm]
definition ab_group_equiv_closed : ab_group B :=
⦃ab_group, group_equiv_closed f,
mul_comm := group_equiv_mul_comm f⦄
end
definition ab_group_of_is_contr (A : Type) [is_contr A] : ab_group A :=
have ab_group unit, from ab_group_unit,
ab_group_equiv_closed (equiv_unit_of_is_contr A)⁻¹ᵉ
definition group_of_is_contr (A : Type) [is_contr A] : group A :=
have ab_group A, from ab_group_of_is_contr A, by apply _
definition ab_group_lift_unit : ab_group (lift unit) :=
ab_group_of_is_contr (lift unit)
definition trivial_ab_group_lift : AbGroup :=
AbGroup.mk _ ab_group_lift_unit
definition homomorphism_of_is_contr_right (A : Group) {B : Type} (H : is_contr B) :
A →g Group.mk B (group_of_is_contr B) :=
group.homomorphism.mk (λa, center _) (λa a', !is_prop.elim)
open trunc pointed is_conn
definition ab_group_homotopy_group_of_is_conn (n : ) (A : Type*) [H : is_conn 1 A] : ab_group (π[n] A) :=
begin
have is_conn 0 A, from !is_conn_of_is_conn_succ,
cases n with n,
{ unfold [homotopy_group, ptrunc], apply ab_group_of_is_contr },
cases n with n,
{ unfold [homotopy_group, ptrunc], apply ab_group_of_is_contr },
exact ab_group_homotopy_group n A
end
end
namespace int /- move to int-/
definition max0 :
| (of_nat n) := n
| (-[1+ n]) := 0
lemma le_max0 : Π(n : ), n ≤ of_nat (max0 n)
| (of_nat n) := proof le.refl n qed
| (-[1+ n]) := proof unit.star qed
lemma le_of_max0_le {n : } {m : } (h : max0 n ≤ m) : n ≤ of_nat m :=
le.trans (le_max0 n) (of_nat_le_of_nat_of_le h)
end int
/- exact couples -/
namespace left_module
@ -172,19 +240,55 @@ namespace left_module
⦃exact_couple, D := D' X, E := E' X, i := i' X, j := j' X, k := k' X,
ij := i'j' X, jk := j'k' X, ki := k'i' X⦄
parameters {R : Ring} {I : Set} (X : exact_couple R I) (B B' : I → )
structure is_bounded {R : Ring} {I : Set} (X : exact_couple R I) : Type :=
(B B' : I → )
(Dub : Π⦃x y⦄ ⦃s : ℕ⦄, (deg (i X))^[s] x = y → B x ≤ s → is_contr (D X y))
(Eub : Π⦃x y⦄ ⦃s : ℕ⦄, (deg (k X))⁻¹ (iterate (deg (i X)) s ((deg (j X))⁻¹ x)) = y →
B x ≤ s → is_contr (E X y))
(Dlb : Π⦃x y z⦄ ⦃s : ℕ⦄ (p : deg (i X) x = y),
iterate (deg (i X)) s y = z → B' z ≤ s → is_surjective (i X ↘ p))
(Elb : Π⦃x y⦄ ⦃s : ℕ⦄, deg (j X) (iterate (deg (i X))⁻¹ᵉ s (deg (k X) x)) = y → B x ≤ s →
is_contr (E X y))
(deg_ik_commute : deg (i X) ∘ deg (k X) ~ deg (k X) ∘ deg (i X))
(Eub : Π⦃x y⦄ ⦃s : ℕ⦄, (deg (i X))^[s] x = y → B x ≤ s → is_contr (E X y))
(Dlb : Π⦃x y z⦄ ⦃s : ℕ⦄ (p : deg (i X) x = y), (deg (i X))^[s] y = z → B' z ≤ s → is_surjective (i X ↘ p))
(Elb : Π⦃x y⦄ ⦃s : ℕ⦄, (deg (i X))⁻¹ᵉ^[s] x = y → B x ≤ s → is_contr (E X y))
(deg_ik_commute : hsquare (deg (k X)) (deg (k X)) (deg (i X)) (deg (i X)))
(deg_ij_commute : hsquare (deg (j X)) (deg (j X)) (deg (i X)) (deg (i X)))
definition deg_iterate_ik_commute (n : ) (x : I) :
(deg (i X))^[n] (deg (k X) x) = deg (k X) ((deg (i X))^[n] x) :=
iterate_commute _ deg_ik_commute x
-- definition is_bounded.mk_commute {R : Ring} {I : Set} {X : exact_couple R I}
-- (B B' : I → )
-- (Dub : Π⦃x : I⦄ ⦃s : ℕ⦄, B x ≤ s → is_contr (D X ((deg (i X))^[s] x)))
-- (Eub : Π⦃x : I⦄ ⦃s : ℕ⦄, B x ≤ s → is_contr (E X ((deg (i X))^[s] x)))
-- (Dlb : Π⦃x : I⦄ ⦃s : ℕ⦄, B' x ≤ s → is_surjective (i X (((deg (i X))⁻¹ᵉ^[s + 1] x))))
-- (Elb : Π⦃x : I⦄ ⦃s : ℕ⦄, B x ≤ s → is_contr (E X ((deg (i X))⁻¹ᵉ^[s] x)))
-- (deg_ik_commute : deg (i X) ∘ deg (k X) ~ deg (k X) ∘ deg (i X))
-- (deg_ij_commute : deg (i X) ∘ deg (j X) ~ deg (j X) ∘ deg (i X)) : is_bounded X :=
-- begin
-- apply is_bounded.mk B B',
-- { intro x y s p h, induction p, exact Dub h },
-- { intro x y s p h, induction p,
-- refine @(is_contr_middle_of_is_exact (exact_couple.jk X (right_inv (deg (j X)) _) idp)) _ _ _,
-- --refine transport (λx, is_contr (E X x)) _ (Eub h), exact sorry
-- },
-- { exact sorry },
-- { exact sorry },
-- { assumption },
-- end
open is_bounded
parameters {R : Ring} {I : Set} (X : exact_couple R I) (HH : is_bounded X)
local abbreviation B := B HH
local abbreviation B' := B' HH
local abbreviation Dub := Dub HH
local abbreviation Eub := Eub HH
local abbreviation Dlb := Dlb HH
local abbreviation Elb := Elb HH
local abbreviation deg_ik_commute := deg_ik_commute HH
local abbreviation deg_ij_commute := deg_ij_commute HH
definition deg_iterate_ik_commute (n : ) :
hsquare (deg (k X)) (deg (k X)) ((deg (i X))^[n]) ((deg (i X))^[n]) :=
iterate_commute n deg_ik_commute
definition deg_iterate_ij_commute (n : ) :
hsquare (deg (j X)) (deg (j X)) ((deg (i X))⁻¹ᵉ^[n]) ((deg (i X))⁻¹ᵉ^[n]) :=
iterate_commute n (hvinverse deg_ij_commute)
-- we start counting pages at 0, not at 2.
definition page (r : ) : exact_couple R I :=
@ -236,13 +340,19 @@ namespace left_module
(deg (d (page r)))⁻¹ ~ (deg (k X))⁻¹ ∘ iterate (deg (i X)) r ∘ (deg (j X))⁻¹ :=
compose2 (to_inv_homotopy_to_inv (deg_k r)) (deg_j_inv r)
definition B2 (x : I) : :=
max (B (deg (j X) (deg (k X) x))) (B ((deg (k X))⁻¹ ((deg (j X))⁻¹ x)))
include Elb Eub
definition Estable {x : I} {r : } (H : B x ≤ r) :
definition Estable {x : I} {r : } (H : B2 x ≤ r) :
E (page (r + 1)) x ≃lm E (page r) x :=
begin
change homology (d (page r) x) (d (page r) ← x) ≃lm E (page r) x,
apply homology_isomorphism: apply is_contr_E,
exact Eub (deg_d_inv r x)⁻¹ H, exact Elb (deg_d r x)⁻¹ H
exact Eub (hhinverse (deg_iterate_ik_commute r) _ ⬝ (deg_d_inv r x)⁻¹)
(le.trans !le_max_right H),
exact Elb (deg_iterate_ij_commute r _ ⬝ (deg_d r x)⁻¹)
(le.trans !le_max_left H)
end
include Dlb
@ -269,31 +379,29 @@ namespace left_module
end
definition Einf : graded_module R I :=
λx, E (page (B x)) x
λx, E (page (B2 x)) x
definition Dinf : graded_module R I :=
λx, D (page (B' x)) x
definition Einfstable {x y : I} {r : } (Hr : B y ≤ r) (p : x = y) :
Einf y ≃lm E (page r) x :=
definition Einfstable {x y : I} {r : } (Hr : B2 y ≤ r) (p : x = y) : Einf y ≃lm E (page r) x :=
by symmetry; induction p; induction Hr with r Hr IH; reflexivity; exact Estable Hr ⬝lm IH
definition Dinfstable {x y : I} {r : } (Hr : B' y ≤ r) (p : x = y) :
Dinf y ≃lm D (page r) x :=
definition Dinfstable {x y : I} {r : } (Hr : B' y ≤ r) (p : x = y) : Dinf y ≃lm D (page r) x :=
by symmetry; induction p; induction Hr with r Hr IH; reflexivity; exact Dstable Hr ⬝lm IH
parameters {x : I}
definition r (n : ) : :=
max (max (B x + n + 1) (B ((deg (i X))^[n] x)))
max (max (B (deg (j X) (deg (k X) x)) + n + 1) (B2 ((deg (i X))^[n] x)))
(max (B' (deg (k X) ((deg (i X))^[n] x)))
(max (B' (deg (k X) ((deg (i X))^[n+1] x))) (B ((deg (j X))⁻¹ ((deg (i X))^[n] x)))))
lemma rb0 (n : ) : r n ≥ n + 1 :=
ge.trans !le_max_left (ge.trans !le_max_left !le_add_left)
lemma rb1 (n : ) : B x ≤ r n - (n + 1) :=
lemma rb1 (n : ) : B (deg (j X) (deg (k X) x)) ≤ r n - (n + 1) :=
le_sub_of_add_le (le.trans !le_max_left !le_max_left)
lemma rb2 (n : ) : B ((deg (i X))^[n] x) ≤ r n :=
lemma rb2 (n : ) : B2 ((deg (i X))^[n] x) ≤ r n :=
le.trans !le_max_right !le_max_left
lemma rb3 (n : ) : B' (deg (k X) ((deg (i X))^[n] x)) ≤ r n :=
le.trans !le_max_left !le_max_right
@ -321,6 +429,7 @@ namespace left_module
{ exact j (page (r n)) _ },
{ apply is_contr_D, refine Dub !deg_j_inv⁻¹ (rb5 n) },
{ apply is_contr_E, refine Elb _ (rb1 n),
refine !deg_iterate_ij_commute ⬝ _,
refine ap (deg (j X)) _ ⬝ !deg_j⁻¹,
refine iterate_sub _ !rb0 _ ⬝ _, apply ap (_^[r n]),
exact ap (deg (i X)) (!deg_iterate_ik_commute ⬝ !deg_k⁻¹) ⬝ !deg_i⁻¹ },
@ -346,51 +455,13 @@ namespace left_module
end
end left_module
open left_module
namespace pointed
-- move
open pointed int group is_trunc trunc is_conn
section
variables {A B : Type} (f : A ≃ B) [ab_group A]
-- to group
definition group_equiv_mul_comm (b b' : B) : group_equiv_mul f b b' = group_equiv_mul f b' b :=
by rewrite [↑group_equiv_mul, mul.comm]
definition ab_group_equiv_closed : ab_group B :=
⦃ab_group, group_equiv_closed f,
mul_comm := group_equiv_mul_comm f⦄
end
definition ab_group_of_is_contr (A : Type) [is_contr A] : ab_group A :=
have ab_group unit, from ab_group_unit,
ab_group_equiv_closed (equiv_unit_of_is_contr A)⁻¹ᵉ
definition group_of_is_contr (A : Type) [is_contr A] : group A :=
have ab_group A, from ab_group_of_is_contr A, by apply _
definition ab_group_lift_unit : ab_group (lift unit) :=
ab_group_of_is_contr (lift unit)
definition trivial_ab_group_lift : AbGroup :=
AbGroup.mk _ ab_group_lift_unit
definition homomorphism_of_is_contr_right (A : Group) {B : Type} (H : is_contr B) :
A →g Group.mk B (group_of_is_contr B) :=
group.homomorphism.mk (λa, center _) (λa a', !is_prop.elim)
definition ab_group_homotopy_group_of_is_conn (n : ) (A : Type*) [H : is_conn 1 A] : ab_group (π[n] A) :=
begin
have is_conn 0 A, from !is_conn_of_is_conn_succ,
cases n with n,
{ unfold [homotopy_group, ptrunc], apply ab_group_of_is_contr },
cases n with n,
{ unfold [homotopy_group, ptrunc], apply ab_group_of_is_contr },
exact ab_group_homotopy_group n A
end
definition homotopy_group_conn_nat (n : ) (A : Type*[1]) : AbGroup :=
AbGroup.mk (π[n] A) (ab_group_homotopy_group_of_is_conn n A)
@ -437,19 +508,6 @@ end pointed
namespace spectrum
open pointed int group is_trunc trunc is_conn prod prod.ops group fin chain_complex
section
-- notation `πₛ→[`:95 n:0 `]`:0 := shomotopy_group_fun n
definition is_equiv_mul_right [constructor] {A : Group} (a : A) : is_equiv (λb, b * a) :=
adjointify _ (λb : A, b * a⁻¹) (λb, !inv_mul_cancel_right) (λb, !mul_inv_cancel_right)
definition right_action [constructor] {A : Group} (a : A) : A ≃ A :=
equiv.mk _ (is_equiv_mul_right a)
definition is_equiv_add_right [constructor] {A : AddGroup} (a : A) : is_equiv (λb, b + a) :=
adjointify _ (λb : A, b - a) (λb, !neg_add_cancel_right) (λb, !add_neg_cancel_right)
definition add_right_action [constructor] {A : AddGroup} (a : A) : A ≃ A :=
equiv.mk _ (is_equiv_add_right a)
parameters {A : → spectrum} (f : Π(s : ), A s →ₛ A (s - 1))
@ -467,8 +525,6 @@ namespace spectrum
fapply graded_hom.mk, exact (prod_equiv_prod erfl (add_right_action (- 1))),
intro v, induction v with n s,
apply lm_hom_int.mk, esimp,
-- exact homomorphism.mk _ (is_mul_hom_LES_of_shomotopy_groups (f s) (n, 0)),
-- exact shomotopy_groups_fun (f s) (n, 0)
exact πₛ→[n] (f s)
end
@ -486,42 +542,90 @@ namespace spectrum
fapply graded_hom.mk erfl,
intro v, induction v with n s,
apply lm_hom_int.mk, esimp,
-- exact homomorphism.mk _ (is_mul_hom_LES_of_shomotopy_groups (f s) (n, 1)),
-- exact shomotopy_groups_fun (f s) (n, 1)
exact πₛ→[n] (spoint (f s))
end
lemma ij_sequence : is_exact_gmod i_sequence j_sequence :=
begin
intro i, induction i with n s,
revert n, refine equiv_rect (add_right_action 1) _ _, intro n,
esimp, intro j k p, unfold [i_sequence] at p,
-- induction p,
intro q, unfold [j_sequence] at q,
note qq := left_inv (deg j_sequence) (n, s),
unfold [j_sequence] at qq,
revert k q,
--refine eq.rec_to2 qq _ _
--intro i j k p q,
-- revert k q,
intro x y z p q,
revert y z q p,
refine eq.rec_right_inv (deg j_sequence) _,
intro y, induction x with n s, induction y with m t,
refine equiv_rect !dpair_eq_dpair_equiv⁻¹ᵉ _ _,
intro pq, esimp at pq, induction pq with p q,
revert t q, refine eq.rec_equiv (add_right_action (- 1)) _,
induction p using eq.rec_symm,
apply is_exact_homotopy homotopy.rfl,
{ symmetry, intro, apply graded_hom_mk_out'_left_inv },
rexact is_exact_of_is_exact_at (is_exact_LES_of_shomotopy_groups (f s) (m, 2)),
-- exact sorry
end
lemma jk_sequence : is_exact_gmod j_sequence k_sequence :=
sorry
begin
intro x y z p q, induction q,
revert x y p, refine eq.rec_right_inv (deg j_sequence) _,
intro x, induction x with n s,
apply is_exact_homotopy,
{ symmetry, intro, apply graded_hom_mk_out'_left_inv },
{ reflexivity },
rexact is_exact_of_is_exact_at (is_exact_LES_of_shomotopy_groups (f s) (n, 1)),
end
local attribute i_sequence [reducible]
lemma ki_sequence : is_exact_gmod k_sequence i_sequence :=
begin
-- unfold [is_exact_gmod, is_exact_mod],
intro i j k p q, induction p, induction q, induction i with n s,
rexact is_exact_of_is_exact_at (is_exact_LES_of_shomotopy_groups (f s) (n, 0)),
end
definition exact_couple_sequence : exact_couple r I :=
definition exact_couple_sequence [constructor] : exact_couple r I :=
exact_couple.mk D_sequence E_sequence i_sequence j_sequence k_sequence ij_sequence jk_sequence ki_sequence
open int
parameters (ub : ) (lb : )
(Aub : Πs n, s ≥ ub → is_contr (A s n))
(Alb : Πs n, s ≤ lb n → is_contr (πₛ[n] (A s)))
definition B : I →
| (n, s) := max0 (s - lb n)
definition B' : I →
| (n, s) := max0 (ub - s)
lemma iterate_deg_i (n s : ) (m : ) : (deg i_sequence)^[m] (n, s) = (n, s - m) :=
begin
induction m with m IH,
{ exact prod_eq idp !sub_zero⁻¹ },
{ exact ap (deg i_sequence) IH ⬝ (prod_eq idp !sub_sub) }
end
include Aub Alb
lemma Dub ⦃x : I⦄ ⦃t : ℕ⦄ (h : B x ≤ t) : is_contr (D_sequence ((deg i_sequence)^[t] x)) :=
begin
-- apply is_contr_homotopy_group_of_is_contr,
apply Alb, induction x with n s, rewrite [iterate_deg_i],
apply sub_le_of_sub_le,
exact le_of_max0_le h,
end
lemma Eub ⦃x : I⦄ ⦃s : ℕ⦄ (H : B x ≤ s) : is_contr (E_sequence ((deg i_sequence)^[s] x)) :=
begin
exact sorry
end
lemma Dlb ⦃x : I⦄ ⦃s : ℕ⦄ (H : B' x ≤ s) : is_surjective (i_sequence ((deg i_sequence)⁻¹ᵉ^[s+1] x)) :=
begin
exact sorry
end
lemma Elb ⦃x : I⦄ ⦃s : ℕ⦄ (H : B x ≤ s) : is_contr (E_sequence ((deg i_sequence)⁻¹ᵉ^[s] x)) :=
begin
exact sorry
end
-- definition is_bounded_sequence : is_bounded exact_couple_sequence :=
-- is_bounded.mk_commute B B' Dub Eub Dlb Elb (by reflexivity) sorry
end

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@ -28,6 +28,24 @@ definition is_exact_g.mk {A B C : Group} {f : A →g B} {g : B →g C}
(H₁ : Πa, g (f a) = 1) (H₂ : Πb, g b = 1 → image f b) : is_exact_g f g :=
is_exact.mk H₁ H₂
-- TO DO: give less univalency proof
definition is_exact_homotopy {A B : Type} {C : Type*} {f f' : A → B} {g g' : B → C}
(p : f ~ f') (q : g ~ g') (H : is_exact f g) : is_exact f' g' :=
begin
induction p using homotopy.rec_on_idp,
induction q using homotopy.rec_on_idp,
exact H
end
definition is_contr_middle_of_is_exact {A B : Type} {C : Type*} {f : A → B} {g : B → C} (H : is_exact f g)
[is_contr A] [is_set B] [is_contr C] : is_contr B :=
begin
apply is_contr.mk (f pt),
intro b,
induction is_exact.ker_in_im H b !is_prop.elim,
exact ap f !is_prop.elim ⬝ p
end
namespace algebra
definition ab_group_unit [constructor] : ab_group unit :=
⦃ab_group, trivial_group, mul_comm := λx y, idp⦄
@ -80,6 +98,38 @@ namespace eq
induction p₀, induction p', induction p, exact H
end
definition eq.rec_right_inv {A : Type} (f : A ≃ A) {P : Π⦃a₀ a₁⦄, f a₀ = a₁ → Type}
(H : Πa, P (right_inv f a)) ⦃a₀ a₁ : A⦄ (p : f a₀ = a₁) : P p :=
begin
revert a₀ p, refine equiv_rect f⁻¹ᵉ _ _,
intro a₀ p, exact eq.rec_to (right_inv f a₀) (H a₀) p,
end
definition eq.rec_equiv {A B : Type} {a₀ : A} (f : A ≃ B) {P : Π⦃a₁⦄, f a₀ = f a₁ → Type}
(H : P (idpath (f a₀))) ⦃a₁ : A⦄ (p : f a₀ = f a₁) : P p :=
begin
-- induction f using equiv.rec_on_ua_idp, esimp at *, induction p, exact H
revert a₁ p, refine equiv_rect f⁻¹ᵉ _ _, intro b p,
refine transport (@P _) (!con_inv_cancel_right) _,
exact b, exact right_inv f b,
generalize p ⬝ right_inv f b,
clear p, intro q, induction q,
exact sorry
end
definition eq.rec_symm {A : Type} {a₀ : A} {P : Π⦃a₁⦄, a₁ = a₀ → Type}
(H : P idp) ⦃a₁ : A⦄ (p : a₁ = a₀) : P p :=
begin
cases p, exact H
end
definition is_contr_homotopy_group_of_is_contr (A : Type*) (n : ) [is_contr A] : is_contr (π[n] A) :=
begin
apply is_trunc_trunc_of_is_trunc,
apply is_contr_loop_of_is_trunc,
apply is_trunc_of_is_contr
end
section -- squares
variables {A B : Type} {a a' a'' a₀₀ a₂₀ a₄₀ a₀₂ a₂₂ a₂₄ a₀₄ a₄₂ a₄₄ a₁ a₂ a₃ a₄ : A}
/-a₀₀-/ {p₁₀ p₁₀' : a₀₀ = a₂₀} /-a₂₀-/ {p₃₀ : a₂₀ = a₄₀} /-a₄₀-/