61 lines
2.3 KiB
Text
61 lines
2.3 KiB
Text
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import algebra.group_theory ..move_to_lib
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open pi pointed algebra group eq equiv is_trunc
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namespace group
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/- Group of functions whose codomain is a group -/
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definition group_arrow [instance] (A B : Type) [group B] : group (A → B) :=
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begin
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fapply group.mk,
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{ intro f g a, exact f a * g a },
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{ apply is_trunc_arrow },
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{ intros, apply eq_of_homotopy, intro a, apply mul.assoc },
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{ intro a, exact 1 },
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{ intros, apply eq_of_homotopy, intro a, apply one_mul },
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{ intros, apply eq_of_homotopy, intro a, apply mul_one },
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{ intro f a, exact (f a)⁻¹ },
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{ intros, apply eq_of_homotopy, intro a, apply mul.left_inv }
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end
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definition Group_arrow (A : Type) (G : Group) : Group :=
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Group.mk (A → G) _
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definition comm_group_arrow [instance] (A B : Type) [comm_group B] : comm_group (A → B) :=
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⦃comm_group, group_arrow A B,
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mul_comm := by intros; apply eq_of_homotopy; intro a; apply mul.comm⦄
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definition CommGroup_arrow (A : Type) (G : CommGroup) : CommGroup :=
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CommGroup.mk (A → G) _
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definition pgroup_ppmap [instance] (A B : Type*) [pgroup B] : pgroup (ppmap A B) :=
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begin
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fapply pgroup.mk,
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{ intro f g, apply pmap.mk (λa, f a * g a),
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exact ap011 mul (respect_pt f) (respect_pt g) ⬝ !one_mul },
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{ apply is_trunc_pmap },
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{ intros, apply pmap_eq_of_homotopy, intro a, apply mul.assoc },
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{ intro f, apply pmap.mk (λa, (f a)⁻¹), apply inv_eq_one, apply respect_pt },
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{ intros, apply pmap_eq_of_homotopy, intro a, apply one_mul },
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{ intros, apply pmap_eq_of_homotopy, intro a, apply mul_one },
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{ intros, apply pmap_eq_of_homotopy, intro a, apply mul.left_inv }
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end
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definition Group_pmap (A : Type*) (G : Group) : Group :=
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Group_of_pgroup (ppmap A (pType_of_Group G))
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definition CommGroup_pmap (A : Type*) (G : CommGroup) : CommGroup :=
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CommGroup.mk (A →* pType_of_Group G)
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⦃ comm_group, Group.struct (Group_pmap A G),
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mul_comm := by intro f g; apply pmap_eq_of_homotopy; intro a; apply mul.comm ⦄
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definition Group_pmap_homomorphism [constructor] {A A' : Type*} (f : A' →* A) (G : CommGroup) :
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Group_pmap A G →g Group_pmap A' G :=
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begin
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fapply homomorphism.mk,
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{ intro g, exact g ∘* f},
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{ intro g h, apply pmap_eq_of_homotopy, intro a, reflexivity }
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end
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end group
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