69 lines
2.3 KiB
Text
69 lines
2.3 KiB
Text
/-
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Copyright (c) 2016 Egbert Rijke. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Egbert Rijke
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Exact couple, derived couples, and so on
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-/
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import algebra.group_theory hit.set_quotient types.sigma types.list types.sum .quotient_group .subgroup
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open eq algebra is_trunc set_quotient relation sigma sigma.ops prod prod.ops sum list trunc function group trunc
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equiv
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structure is_exact {A B C : CommGroup} (f : A →g B) (g : B →g C) :=
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( im_in_ker : Π(a:A), g (f a) = 1)
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( ker_in_im : Π(b:B), (g b = 1) → ∃(a:A), f a = b)
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definition is_boundary {B : CommGroup} (d : B →g B) := Π(b:B), d (d b) = 1
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definition image_subgroup_of_bd {B : CommGroup} (d : B →g B) (H : is_boundary d) : subgroup_rel (comm_kernel d) :=
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subgroup_rel_of_subgroup (image_subgroup d) (kernel_subgroup d)
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begin
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intro g p,
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induction p with f, induction f with h p,
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rewrite [p⁻¹],
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esimp,
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exact H h
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end
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definition homology {B : CommGroup} (d : B →g B) (H : is_boundary d) : CommGroup :=
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@quotient_comm_group (comm_kernel d) (image_subgroup_of_bd d H)
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structure exact_couple (A B : CommGroup) : Type :=
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( i : A →g A) (j : A →g B) (k : B →g A)
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( exact_ij : is_exact i j)
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( exact_jk : is_exact j k)
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( exact_ki : is_exact k i)
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definition boundary {A B : CommGroup} (CC : exact_couple A B) : B →g B :=
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(exact_couple.j CC) ∘g (exact_couple.k CC)
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definition boundary_is_boundary {A B : CommGroup} (CC : exact_couple A B) : is_boundary (boundary CC) :=
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begin
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induction CC,
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induction exact_jk,
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intro b,
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exact (ap (group_fun j) (im_in_ker (group_fun k b))) ⬝ (respect_one j)
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end
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section derived_couple
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variables {A B : CommGroup} (CC : exact_couple A B)
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definition derived_couple_A : CommGroup :=
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comm_subgroup (image_subgroup (exact_couple.i CC))
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definition derived_couple_B : CommGroup :=
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homology (boundary CC) (boundary_is_boundary CC)
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definition derived_couple_i : derived_couple_A CC →g derived_couple_A CC :=
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(image_lift (exact_couple.i CC)) ∘g (image_incl (exact_couple.i CC))
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definition derived_couple_j : derived_couple_A CC →g derived_couple_B CC :=
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begin
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-- refine (comm_gq_map (comm_kernel (boundary CC)) (image_subgroup_of_bd (boundary CC) (boundary_is_boundary CC))) ∘g _,
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exact sorry
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end
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end derived_couple
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