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started on derived couple

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This commit is contained in:
Steve Awodey 2017-04-07 15:05:10 -04:00
parent f76e665dd3
commit 200885ad21
1 changed files with 8 additions and 0 deletions
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8
algebra/exact_couple.hlean
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@ -26,6 +26,14 @@ definition image_subgroup_of_diff {B : AbGroup} (d : B →g B) (H : is_different
definition homology {B : AbGroup} (d : B →g B) (H : is_differential d) : AbGroup :=
@quotient_ab_group (ab_kernel d) (image_subgroup_of_diff d H)
definition SES_of_differential {B : AbGroup} (d : B →g B) (H : is_differential d) : SES (ab_image d) (ab_kernel d) (homology d H) :=
begin
fapply SES.mk,
sorry,
-- use the more general fact that a subgroup inclusion is a group homomorphism
-- maybe use SES_of_subgroup?
end
structure exact_couple (A B : AbGroup) : Type :=
( i : A →g A) (j : A →g B) (k : B →g A)
( exact_ij : is_exact i j)