Spectral/pointed_pi.hlean
Floris van Doorn cfdfa0f22a Work on the fact that pointed dependent products preserve fibration sequences
We now define pointed homotopies as dependent pointed maps, and have some properties about pointed sigmas
2017-06-19 02:03:54 -04:00

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/-
Copyright (c) 2016 Ulrik Buchholtz. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Ulrik Buchholtz, Floris van Doorn
-/
import homotopy.connectedness types.pointed2
open eq pointed equiv sigma is_equiv
/-
In this file we define dependent pointed maps and properties of them.
Using this, we give the truncation level
of the type of pointed maps, giving the connectivity of
the domain and the truncation level of the codomain.
This is is_trunc_pmap_of_is_conn at the end.
We also prove other properties about pointed (dependent maps), like the fact that
(Π*a, F a) → (Π*a, X a) → (Π*a, B a)
is a fibration sequence if (F a) → (X a) → B a) is.
-/
namespace pointed
definition pointed_respect_pt [instance] [constructor] {A B : Type*} (f : A →* B) :
pointed (f pt = pt) :=
pointed.mk (respect_pt f)
definition ppi_gen_of_phomotopy [constructor] {A B : Type*} {f g : A →* B} (h : f ~* g) :
ppi_gen (λx, f x = g x) (respect_pt f ⬝ (respect_pt g)⁻¹) :=
h
abbreviation ppi_resp_pt [unfold 3] := @ppi.resp_pt
definition ppi_const [constructor] {A : Type*} (P : A → Type*) : ppi P :=
ppi.mk (λa, pt) idp
definition pointed_ppi [instance] [constructor] {A : Type*}
(P : A → Type*) : pointed (ppi P) :=
pointed.mk (ppi_const P)
definition pppi [constructor] {A : Type*} (P : A → Type*) : Type* :=
pointed.mk' (ppi P)
notation `Π*` binders `, ` r:(scoped P, pppi P) := r
definition ppi_homotopy {A : Type*} {P : A → Type} {x : P pt} (f g : ppi_gen P x) : Type :=
ppi_gen (λa, f a = g a) (ppi_gen.resp_pt f ⬝ (ppi_gen.resp_pt g)⁻¹)
variables {A : Type*} {P Q R : A → Type*} {f g h : Π*a, P a}
{B : A → Type} {x₀ : B pt} {k l m : ppi_gen B x₀}
infix ` ~~* `:50 := ppi_homotopy
definition ppi_homotopy.mk [constructor] [reducible] (h : k ~ l)
(p : h pt ⬝ ppi_gen.resp_pt l = ppi_gen.resp_pt k) : k ~~* l :=
ppi_gen.mk h (eq_con_inv_of_con_eq p)
definition ppi_to_homotopy [coercion] [unfold 6] [reducible] (p : k ~~* l) : Πa, k a = l a := p
definition ppi_to_homotopy_pt [unfold 6] [reducible] (p : k ~~* l) :
p pt ⬝ ppi_gen.resp_pt l = ppi_gen.resp_pt k :=
con_eq_of_eq_con_inv (ppi_gen.resp_pt p)
variable (k)
protected definition ppi_homotopy.refl : k ~~* k :=
sorry
variable {k}
protected definition ppi_homotopy.rfl [refl] : k ~~* k :=
ppi_homotopy.refl k
protected definition ppi_homotopy.symm [symm] (p : k ~~* l) : l ~~* k :=
sorry
protected definition ppi_homotopy.trans [trans] (p : k ~~* l) (q : l ~~* m) : k ~~* m :=
sorry
infix ` ⬝*' `:75 := ppi_homotopy.trans
postfix `⁻¹*'`:(max+1) := ppi_homotopy.symm
definition ppi_equiv_pmap (A B : Type*) : (Π*(a : A), B) ≃ (A →* B) :=
begin
fapply equiv.MK,
{ intro k, induction k with k p, exact pmap.mk k p },
{ intro k, induction k with k p, exact ppi.mk k p },
{ intro k, induction k with k p, reflexivity },
{ intro k, induction k with k p, reflexivity }
end
definition pppi_pequiv_ppmap (A B : Type*) : (Π*(a : A), B) ≃* ppmap A B :=
pequiv_of_equiv (ppi_equiv_pmap A B) idp
definition ppi.sigma_char [constructor] {A : Type*} (B : A → Type*)
: (Π*(a : A), B a) ≃ Σ(k : (Π (a : A), B a)), k pt = pt :=
begin
fapply equiv.MK : intros k,
{ exact ⟨ k , ppi_resp_pt k ⟩ },
all_goals cases k with k p,
{ exact ppi.mk k p },
all_goals reflexivity
end
protected definition ppi_gen.sigma_char [constructor] {A : Type*} (B : A → Type) (b₀ : B pt) :
ppi_gen B b₀ ≃ Σ(k : Πa, B a), k pt = b₀ :=
begin
fapply equiv.MK: intro x,
{ constructor, exact ppi_gen.resp_pt x },
{ induction x, constructor, assumption },
{ induction x, reflexivity },
{ induction x, reflexivity }
end
variables (k l)
definition ppi_homotopy.rec' [recursor] (B : k ~~* l → Type)
(H : Π(h : k ~ l) (p : h pt ⬝ ppi_gen.resp_pt l = ppi_gen.resp_pt k), B (ppi_homotopy.mk h p))
(h : k ~~* l) : B h :=
begin
induction h with h p,
refine transport (λp, B (ppi_gen.mk h p)) _ (H h (con_eq_of_eq_con_inv p)),
apply to_left_inv !eq_con_inv_equiv_con_eq p
end
definition ppi_homotopy.sigma_char [constructor]
: (k ~~* l) ≃ Σ(p : k ~ l), p pt ⬝ ppi_gen.resp_pt l = ppi_gen.resp_pt k :=
begin
fapply equiv.MK : intros h,
{ exact ⟨h , ppi_to_homotopy_pt h⟩ },
{ cases h with h p, exact ppi_homotopy.mk h p },
{ cases h with h p, exact ap (dpair h) (to_right_inv !eq_con_inv_equiv_con_eq p) },
{ induction h using ppi_homotopy.rec' with h p,
exact ap (ppi_homotopy.mk h) (to_right_inv !eq_con_inv_equiv_con_eq p) }
end
-- the same as pmap_eq_equiv
definition ppi_eq_equiv : (k = l) ≃ (k ~~* l) :=
calc (k = l) ≃ ppi_gen.sigma_char B x₀ k = ppi_gen.sigma_char B x₀ l
: eq_equiv_fn_eq (ppi_gen.sigma_char B x₀) k l
... ≃ Σ(p : k = l),
pathover (λh, h pt = x₀) (ppi_gen.resp_pt k) p (ppi_gen.resp_pt l)
: sigma_eq_equiv _ _
... ≃ Σ(p : k = l),
ppi_gen.resp_pt k = ap (λh, h pt) p ⬝ ppi_gen.resp_pt l
: sigma_equiv_sigma_right
(λp, eq_pathover_equiv_Fl p (ppi_gen.resp_pt k) (ppi_gen.resp_pt l))
... ≃ Σ(p : k = l),
ppi_gen.resp_pt k = apd10 p pt ⬝ ppi_gen.resp_pt l
: sigma_equiv_sigma_right
(λp, equiv_eq_closed_right _ (whisker_right _ (ap_eq_apd10 p _)))
... ≃ Σ(p : k ~ l), ppi_gen.resp_pt k = p pt ⬝ ppi_gen.resp_pt l
: sigma_equiv_sigma_left' eq_equiv_homotopy
... ≃ Σ(p : k ~ l), p pt ⬝ ppi_gen.resp_pt l = ppi_gen.resp_pt k
: sigma_equiv_sigma_right (λp, eq_equiv_eq_symm _ _)
... ≃ (k ~~* l) : ppi_homotopy.sigma_char k l
variables
-- the same as pmap_eq
variables {k l}
definition ppi_eq (h : k ~~* l) : k = l :=
(ppi_eq_equiv k l)⁻¹ᵉ h
definition eq_of_ppi_homotopy (h : k ~~* l) : k = l := ppi_eq h
definition ppi_homotopy_of_eq (p : k = l) : k ~~* l := ppi_eq_equiv k l p
definition ppi_homotopy_of_eq_of_ppi_homotopy (h : k ~~* l) :
ppi_homotopy_of_eq (eq_of_ppi_homotopy h) = h :=
to_right_inv (ppi_eq_equiv k l) h
definition ppi_loop_equiv_lemma (p : k ~ k)
: (p pt ⬝ ppi_gen.resp_pt k = ppi_gen.resp_pt k) ≃ (p pt = idp) :=
calc (p pt ⬝ ppi_gen.resp_pt k = ppi_gen.resp_pt k)
≃ (p pt ⬝ ppi_gen.resp_pt k = idp ⬝ ppi_gen.resp_pt k)
: equiv_eq_closed_right (p pt ⬝ ppi_gen.resp_pt k) (inverse (idp_con (ppi_gen.resp_pt k)))
... ≃ (p pt = idp)
: eq_equiv_con_eq_con_right
variables (k l)
definition ppi_loop_equiv : (k = k) ≃ Π*(a : A), Ω (pType.mk (B a) (k a)) :=
calc (k = k) ≃ (k ~~* k)
: ppi_eq_equiv
... ≃ Σ(p : k ~ k), p pt ⬝ ppi_gen.resp_pt k = ppi_gen.resp_pt k
: ppi_homotopy.sigma_char k k
... ≃ Σ(p : k ~ k), p pt = idp
: sigma_equiv_sigma_right
(λ p, ppi_loop_equiv_lemma p)
... ≃ Π*(a : A), pType.mk (k a = k a) idp
: ppi.sigma_char
... ≃ Π*(a : A), Ω (pType.mk (B a) (k a))
: erfl
variables {k l}
-- definition eq_of_ppi_homotopy (h : k ~~* l) : k = l :=
-- (ppi_eq_equiv k l)⁻¹ᵉ h
definition ppi_loop_pequiv : Ω (Π*(a : A), P a) ≃* Π*(a : A), Ω (P a) :=
pequiv_of_equiv (ppi_loop_equiv pt) idp
definition pmap_compose_ppi [constructor] (g : Π(a : A), ppmap (P a) (Q a))
(f : Π*(a : A), P a) : Π*(a : A), Q a :=
proof ppi.mk (λa, g a (f a)) (ap (g pt) (ppi.resp_pt f) ⬝ respect_pt (g pt)) qed
definition pmap_compose_ppi_const_right (g : Π(a : A), ppmap (P a) (Q a)) :
pmap_compose_ppi g (ppi_const P) ~~* ppi_const Q :=
proof ppi_homotopy.mk (λa, respect_pt (g a)) !idp_con⁻¹ qed
definition pmap_compose_ppi_const_left (f : Π*(a : A), P a) :
pmap_compose_ppi (λa, pconst (P a) (Q a)) f ~~* ppi_const Q :=
sorry
definition ppi_compose_left [constructor] (g : Π(a : A), ppmap (P a) (Q a)) :
(Π*(a : A), P a) →* Π*(a : A), Q a :=
pmap.mk (pmap_compose_ppi g) (ppi_eq (pmap_compose_ppi_const_right g))
definition pmap_compose_ppi_phomotopy_left [constructor] {g g' : Π(a : A), ppmap (P a) (Q a)}
(f : Π*(a : A), P a) (p : Πa, g a ~* g' a) : pmap_compose_ppi g f ~~* pmap_compose_ppi g' f :=
sorry
definition pmap_compose_ppi_pid_left [constructor]
(f : Π*(a : A), P a) : pmap_compose_ppi (λa, pid (P a)) f ~~* f :=
sorry
definition pmap_compose_pmap_compose_ppi [constructor] (h : Π(a : A), ppmap (Q a) (R a))
(g : Π(a : A), ppmap (P a) (Q a)) :
pmap_compose_ppi h (pmap_compose_ppi g f) ~~* pmap_compose_ppi (λa, h a ∘* g a) f :=
sorry
definition ppi_pequiv_right [constructor] (g : Π(a : A), P a ≃* Q a) :
(Π*(a : A), P a) ≃* Π*(a : A), Q a :=
begin
apply pequiv_of_pmap (ppi_compose_left g),
apply adjointify _ (ppi_compose_left (λa, (g a)⁻¹ᵉ*)),
{ intro f, apply ppi_eq,
refine !pmap_compose_pmap_compose_ppi ⬝*' _,
refine pmap_compose_ppi_phomotopy_left _ (λa, !pright_inv) ⬝*' _,
apply pmap_compose_ppi_pid_left },
{ intro f, apply ppi_eq,
refine !pmap_compose_pmap_compose_ppi ⬝*' _,
refine pmap_compose_ppi_phomotopy_left _ (λa, !pleft_inv) ⬝*' _,
apply pmap_compose_ppi_pid_left }
end
definition psigma_gen [constructor] {A : Type*} (P : A → Type) (x : P pt) : Type* :=
pointed.MK (Σa, P a) ⟨pt, x⟩
end pointed
open fiber function
namespace pointed
variables {A B C : Type*}
-- TODO: replace in types.fiber
definition pfiber.sigma_char' (f : A →* B) :
pfiber f ≃* psigma_gen (λa, f a = pt) (respect_pt f) :=
pequiv_of_equiv (fiber.sigma_char f pt) idp
/- the pointed type of unpointed (nondependent) maps -/
definition parrow [constructor] (A : Type) (B : Type*) : Type* :=
pointed.MK (A → B) (const A pt)
/- the pointed type of unpointed dependent maps -/
definition p_pi [constructor] {A : Type} (B : A → Type*) : Type* :=
pointed.MK (Πa, B a) (λa, pt)
definition ppmap.sigma_char (A B : Type*) :
ppmap A B ≃* @psigma_gen (parrow A B) (λf, f pt = pt) idp :=
pequiv_of_equiv pmap.sigma_char idp
definition pppi.sigma_char {A : Type*} {B : A → Type*} :
(Π*(a : A), B a) ≃* @psigma_gen (p_pi B) (λf, f pt = pt) idp :=
proof pequiv_of_equiv !ppi.sigma_char idp qed
definition psigma_gen_pequiv_psigma_gen_right {A : Type*} {B B' : A → Type}
{b : B pt} {b' : B' pt} (f : Πa, B a ≃ B' a) (p : f pt b = b') :
psigma_gen B b ≃* psigma_gen B' b' :=
pequiv_of_equiv (sigma_equiv_sigma_right f) (ap (dpair pt) p)
definition psigma_gen_pequiv_psigma_gen_basepoint {A : Type*} {B : A → Type} {b b' : B pt}
(p : b = b') : psigma_gen B b ≃* psigma_gen B b' :=
psigma_gen_pequiv_psigma_gen_right (λa, erfl) p
definition ppi_gen_functor_right [constructor] {A : Type*} {B B' : A → Type}
{b : B pt} {b' : B' pt} (f : Πa, B a → B' a) (p : f pt b = b') (g : ppi_gen B b)
: ppi_gen B' b' :=
ppi_gen.mk (λa, f a (g a)) (ap (f pt) (ppi_gen.resp_pt g) ⬝ p)
definition ppi_gen_functor_right_compose [constructor] {A : Type*} {B₁ B₂ B₃ : A → Type}
{b₁ : B₁ pt} {b₂ : B₂ pt} {b₃ : B₃ pt} (f₂ : Πa, B₂ a → B₃ a) (p₂ : f₂ pt b₂ = b₃)
(f₁ : Πa, B₁ a → B₂ a) (p₁ : f₁ pt b₁ = b₂)
(g : ppi_gen B₁ b₁) : ppi_gen_functor_right (λa, f₂ a ∘ f₁ a) (ap (f₂ pt) p₁ ⬝ p₂) g ~~*
ppi_gen_functor_right f₂ p₂ (ppi_gen_functor_right f₁ p₁ g) :=
begin
fapply ppi_homotopy.mk,
{ reflexivity },
{ induction p₁, induction p₂, exact !idp_con ⬝ !ap_compose⁻¹ }
end
definition ppi_gen_functor_right_id [constructor] {A : Type*} {B : A → Type}
{b : B pt} (g : ppi_gen B b) : ppi_gen_functor_right (λa, id) idp g ~~* g :=
begin
fapply ppi_homotopy.mk,
{ reflexivity },
{ reflexivity }
end
definition ppi_gen_functor_right_homotopy [constructor] {A : Type*} {B B' : A → Type}
{b : B pt} {b' : B' pt} {f f' : Πa, B a → B' a} {p : f pt b = b'} {p' : f' pt b = b'}
(h : f ~2 f') (q : h pt b ⬝ p' = p) (g : ppi_gen B b) :
ppi_gen_functor_right f p g ~~* ppi_gen_functor_right f' p' g :=
begin
fapply ppi_homotopy.mk,
{ exact λa, h a (g a) },
{ induction g with g r, induction r, induction q,
exact whisker_left _ !idp_con ⬝ !idp_con⁻¹ }
end
definition ppi_gen_equiv_ppi_gen_right [constructor] {A : Type*} {B B' : A → Type}
{b : B pt} {b' : B' pt} (f : Πa, B a ≃ B' a) (p : f pt b = b') :
ppi_gen B b ≃ ppi_gen B' b' :=
equiv.MK (ppi_gen_functor_right f p) (ppi_gen_functor_right (λa, (f a)⁻¹ᵉ) (inv_eq_of_eq p⁻¹))
abstract begin
intro g, apply ppi_eq,
refine !ppi_gen_functor_right_compose⁻¹*' ⬝*' _,
refine ppi_gen_functor_right_homotopy (λa, to_right_inv (f a)) _ g ⬝*'
!ppi_gen_functor_right_id, induction p, exact adj (f pt) b ⬝ ap02 (f pt) !idp_con⁻¹
end end
abstract begin
intro g, apply ppi_eq,
refine !ppi_gen_functor_right_compose⁻¹*' ⬝*' _,
refine ppi_gen_functor_right_homotopy (λa, to_left_inv (f a)) _ g ⬝*'
!ppi_gen_functor_right_id, induction p, exact (!idp_con ⬝ !idp_con)⁻¹,
end end
definition ppi_gen_equiv_ppi_gen_basepoint [constructor] {A : Type*} {B : A → Type} {b b' : B pt}
(p : b = b') : ppi_gen B b ≃ ppi_gen B b' :=
ppi_gen_equiv_ppi_gen_right (λa, erfl) p
definition ppi_psigma {A : Type*} {B : A → Type*} (C : Πa, B a → Type) (c : Πa, C a pt) :
(Π*(a : A), (psigma_gen (C a) (c a))) ≃*
psigma_gen (λ(f : Π*(a : A), B a), ppi_gen (λa, C a (f a))
(transport (C pt) (ppi.resp_pt f)⁻¹ (c pt)))
(ppi_const _) :=
calc (Π*(a : A), psigma_gen (C a) (c a))
≃* @psigma_gen (p_pi (λa, psigma_gen (C a) (c a))) (λf, f pt = pt) idp : pppi.sigma_char
... ≃* psigma_gen (λ(f : Π*(a : A), B a), ppi_gen (λa, C a (f a))
(transport (C pt) (ppi.resp_pt f)⁻¹ (c pt)))
(ppi_const _) : sorry
definition pmap_psigma {A B : Type*} (C : B → Type) (c : C pt) :
ppmap A (psigma_gen C c) ≃*
psigma_gen (λ(f : ppmap A B), ppi_gen (C ∘ f) (transport C (respect_pt f)⁻¹ c))
(ppi_const _) :=
!pppi_pequiv_ppmap⁻¹ᵉ* ⬝e* !ppi_psigma ⬝e* sorry
definition pfiber_ppcompose_left (f : B →* C) :
pfiber (@ppcompose_left A B C f) ≃* ppmap A (pfiber f) :=
calc
pfiber (@ppcompose_left A B C f) ≃*
psigma_gen (λ(g : ppmap A B), f ∘* g = pconst A C)
proof (eq_of_phomotopy (pcompose_pconst f)) qed :
by exact !pfiber.sigma_char'
... ≃* psigma_gen (λ(g : ppmap A B), f ∘* g ~* pconst A C) proof (pcompose_pconst f) qed :
by exact psigma_gen_pequiv_psigma_gen_right (λa, !pmap_eq_equiv)
!phomotopy_of_eq_of_phomotopy
... ≃* psigma_gen (λ(g : ppmap A B), ppi_gen (λa, f (g a) = pt)
(transport (λb, f b = pt) (respect_pt g)⁻¹ (respect_pt f)))
(ppi_const _) :
begin
refine psigma_gen_pequiv_psigma_gen_right
(λg, ppi_gen_equiv_ppi_gen_basepoint (_ ⬝ !eq_transport_Fl⁻¹)) _,
intro g, refine !con_idp ⬝ _, apply whisker_right,
exact ap02 f !inv_inv⁻¹ ⬝ !ap_inv,
apply ppi_eq, fapply ppi_homotopy.mk,
intro x, reflexivity,
refine !idp_con ⬝ _, symmetry, refine !ap_id ◾ !idp_con ⬝ _, apply con.right_inv
end
... ≃* ppmap A (psigma_gen (λb, f b = pt) (respect_pt f)) :
by exact (pmap_psigma _ _)⁻¹ᵉ*
... ≃* ppmap A (pfiber f) : by exact pequiv_ppcompose_left !pfiber.sigma_char'⁻¹ᵉ*
definition pfiber_ppcompose_left_dep {B C : A → Type*} (f : Πa, B a →* C a) :
pfiber (ppi_compose_left f) ≃* Π*(a : A), pfiber (f a) :=
calc
pfiber (ppi_compose_left f) ≃*
psigma_gen (λ(g : Π*(a : A), B a), pmap_compose_ppi f g = ppi_const C)
proof (ppi_eq (pmap_compose_ppi_const_right f)) qed : by exact !pfiber.sigma_char'
... ≃* psigma_gen (λ(g : Π*(a : A), B a), pmap_compose_ppi f g ~~* ppi_const C)
proof (pmap_compose_ppi_const_right f) qed :
by exact psigma_gen_pequiv_psigma_gen_right (λa, !ppi_eq_equiv)
!ppi_homotopy_of_eq_of_ppi_homotopy
... ≃* psigma_gen (λ(g : Π*(a : A), B a), ppi_gen (λa, f a (g a) = pt)
(transport (λb, f pt b = pt) (ppi.resp_pt g)⁻¹ (respect_pt (f pt))))
(ppi_const _) :
begin
refine psigma_gen_pequiv_psigma_gen_right
(λg, ppi_gen_equiv_ppi_gen_basepoint (_ ⬝ !eq_transport_Fl⁻¹)) _,
intro g, refine !con_idp ⬝ _, apply whisker_right,
exact ap02 (f pt) !inv_inv⁻¹ ⬝ !ap_inv,
apply ppi_eq, fapply ppi_homotopy.mk,
intro x, reflexivity,
refine !idp_con ⬝ _, symmetry, refine !ap_id ◾ !idp_con ⬝ _, apply con.right_inv
end
... ≃* Π*(a : A), (psigma_gen (λb, f a b = pt) (respect_pt (f a))) :
by exact (ppi_psigma _ _)⁻¹ᵉ*
... ≃* Π*(a : A), pfiber (f a) : by exact ppi_pequiv_right (λa, !pfiber.sigma_char'⁻¹ᵉ*)
end pointed open pointed
open is_trunc is_conn
namespace is_conn
variables (A : Type*) (n : ℕ₋₂) [H : is_conn (n.+1) A]
include H
definition is_contr_ppi_match (P : A → (n.+1)-Type*)
: is_contr (Π*(a : A), P a) :=
begin
apply is_contr.mk pt,
intro f, induction f with f p,
apply ppi_eq, fapply ppi_homotopy.mk,
{ apply is_conn.elim n, exact p⁻¹ },
{ krewrite (is_conn.elim_β n), apply con.left_inv }
end
definition is_trunc_ppi (k : ℕ₋₂) (P : A → (n.+1+2+k)-Type*)
: is_trunc k.+1 (Π*(a : A), P a) :=
begin
induction k with k IH,
{ apply is_prop_of_imp_is_contr, intro f,
apply is_contr_ppi_match },
{ apply is_trunc_succ_of_is_trunc_loop
(trunc_index.succ_le_succ (trunc_index.minus_two_le k)),
intro f,
apply @is_trunc_equiv_closed_rev _ _ k.+1
(ppi_loop_equiv f),
apply IH, intro a,
apply ptrunctype.mk (Ω (pType.mk (P a) (f a))),
{ apply is_trunc_loop, exact is_trunc_ptrunctype (P a) },
{ exact pt } }
end
definition is_trunc_pmap_of_is_conn (k : ℕ₋₂) (B : (n.+1+2+k)-Type*)
: is_trunc k.+1 (A →* B) :=
@is_trunc_equiv_closed _ _ k.+1 (ppi_equiv_pmap A B)
(is_trunc_ppi A n k (λ a, B))
end is_conn