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[Merged by Bors] - feat(group_theory): subgroups of real numbers #4334

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@PatrickMassot PatrickMassot commented Sep 30, 2020

This fills the last hole in the "Topology of R" section of our undergrad curriculum: additive subgroups of real numbers are either dense or cyclic. Most of this PR is supporting material about ordered abelian groups.

Co-Authored-By: Heather Macbeth 25316162+hrmacbeth@users.noreply.github.com


@PatrickMassot PatrickMassot changed the title Subgroup real feat(group_theory): subgroups of real numbers Sep 30, 2020
@PatrickMassot PatrickMassot added the awaiting-review The author would like community review of the PR label Sep 30, 2020
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@github-actions github-actions bot added the merge-conflict Please `git merge origin/master` then a bot will remove this label. label Sep 30, 2020
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lgtm, modulo trivial stuff
bors d+

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@@ -889,6 +938,9 @@ begin
refine ⟨-n, neg_gsmul x n⟩ }
end

lemma closure_singleton_zero : closure ({0} : set A) = ⊥ :=
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I guess it can't be deduced from closure_singleton_one through to_additive? Even if it can't, it's good to register (after the fact) a to_additive attribute so that later proofs can be converted automatically.

@@ -226,6 +229,9 @@ lemma mem_closure_singleton {x y : A} :
y ∈ closure ({x} : set A) ↔ ∃ n:ℕ, n •ℕ x = y :=
by rw [closure_singleton_eq, add_monoid_hom.mem_mrange]; refl

lemma closure_singleton_zero : closure ({0} : set A) = ⊥ :=
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ditto

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bors bot commented Oct 1, 2020

✌️ PatrickMassot can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

Co-authored-by: sgouezel <sebastien.gouezel@univ-rennes1.fr>
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sgouezel commented Oct 1, 2020

bors r+

@github-actions github-actions bot added ready-to-merge All that is left is for bors to build and merge this PR. (Remember you need to say `bors r+`.) and removed awaiting-review The author would like community review of the PR labels Oct 1, 2020
bors bot pushed a commit that referenced this pull request Oct 1, 2020
This fills the last hole in the "Topology of R" section of our undergrad curriculum: additive subgroups of real numbers are either dense or cyclic. Most of this PR is supporting material about ordered abelian groups. 

Co-Authored-By: Heather Macbeth <25316162+hrmacbeth@users.noreply.github.com>



Co-authored-by: Heather Macbeth <25316162+hrmacbeth@users.noreply.github.com>
Co-authored-by: hrmacbeth <25316162+hrmacbeth@users.noreply.github.com>
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bors bot commented Oct 1, 2020

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(group_theory): subgroups of real numbers [Merged by Bors] - feat(group_theory): subgroups of real numbers Oct 1, 2020
@bors bors bot closed this Oct 1, 2020
@bors bors bot deleted the subgroup_real branch October 1, 2020 22:41
adomani pushed a commit that referenced this pull request Oct 7, 2020
This fills the last hole in the "Topology of R" section of our undergrad curriculum: additive subgroups of real numbers are either dense or cyclic. Most of this PR is supporting material about ordered abelian groups. 

Co-Authored-By: Heather Macbeth <25316162+hrmacbeth@users.noreply.github.com>



Co-authored-by: Heather Macbeth <25316162+hrmacbeth@users.noreply.github.com>
Co-authored-by: hrmacbeth <25316162+hrmacbeth@users.noreply.github.com>
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4 participants