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[Merged by Bors] - feat(group_theory/schreier): The size of the commutator subgroup is bounded in terms of the index of the center and the number of commutators #16679

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@tb65536 tb65536 commented Sep 28, 2022

This PR proves that the size of the commutator subgroup is bounded in terms of the index of the center and the number of commutators. The proof uses Schreier's lemma and the transfer homomorphism.

I included lots of comments since the proof is rather technical. But please let me know if I went overboard.

Ultimately, this is building up to a bound on the size of the commutator subgroup just in terms of the number of commutators.


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@tb65536 tb65536 added awaiting-review The author would like community review of the PR t-algebra Algebra (groups, rings, fields etc) labels Sep 28, 2022
@tb65536 tb65536 changed the title feat(group_theory/abelianization): The size of the commutator subgroup is bounded in terms of the index of the center and the number of commutators feat(group_theory/schreier): The size of the commutator subgroup is bounded in terms of the index of the center and the number of commutators Sep 28, 2022
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LGTM

bors d+

src/group_theory/schreier.lean Outdated Show resolved Hide resolved
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bors bot commented Sep 30, 2022

✌️ tb65536 can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

@leanprover-community-bot-assistant leanprover-community-bot-assistant added delegated The PR author may merge after reviewing final suggestions. and removed awaiting-review The author would like community review of the PR labels Sep 30, 2022
Co-authored-by: Johan Commelin <johan@commelin.net>
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tb65536 commented Oct 1, 2022

bors r+

bors bot pushed a commit that referenced this pull request Oct 1, 2022
…ounded in terms of the index of the center and the number of commutators (#16679)

This PR proves that the size of the commutator subgroup is bounded in terms of the index of the center and the number of commutators. The proof uses Schreier's lemma and the transfer homomorphism.

I included lots of comments since the proof is rather technical. But please let me know if I went overboard.

Ultimately, this is building up to a bound on the size of the commutator subgroup just in terms of the number of commutators.



Co-authored-by: Thomas Browning <tb65536@users.noreply.github.com>
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bors bot commented Oct 1, 2022

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(group_theory/schreier): The size of the commutator subgroup is bounded in terms of the index of the center and the number of commutators [Merged by Bors] - feat(group_theory/schreier): The size of the commutator subgroup is bounded in terms of the index of the center and the number of commutators Oct 1, 2022
@bors bors bot closed this Oct 1, 2022
@bors bors bot deleted the card_commutator_dvd_index_center_pow branch October 1, 2022 03:21
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