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[Merged by Bors] - feat(algebra/star/unitary): (re)define unitary elements of a star monoid #11457

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@dupuisf dupuisf commented Jan 14, 2022

This PR defines unitary R for a star monoid R as the submonoid containing the elements that satisfy both star U * U = 1 and U * star U = 1. We show basic properties (i.e. that this forms a group) and show that they
preserve the norm when R is a C* ring.

Note that this replaces unitary_submonoid, which only included the condition star U * U = 1 -- see the discussion on Zulip.


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@dupuisf dupuisf added the awaiting-review The author would like community review of the PR label Jan 14, 2022
@dupuisf dupuisf changed the title Dupuisf/unitary def feat(algebra/star/unitary): (re)define unitary elements of a star monoid Jan 14, 2022
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I went ahead and pushed my golfing suggestions, since it was easier than adding github comments - hope that's ok!

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LGTM, but since I pushed some golfs someone else should take a quick look (as should you, of course!)

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(@eric-wieser it seems your golfs broke the build)

eric-wieser and others added 3 commits January 14, 2022 23:18
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
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dupuisf commented Jan 15, 2022

LGTM, but since I pushed some golfs someone else should take a quick look (as should you, of course!)

Thanks -- the changes look good!

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bors d+
Thanks!

src/algebra/star/unitary.lean Outdated Show resolved Hide resolved
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bors bot commented Jan 16, 2022

✌️ dupuisf 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 the delegated The PR author may merge after reviewing final suggestions. label Jan 16, 2022
@leanprover-community-bot-assistant leanprover-community-bot-assistant removed the awaiting-review The author would like community review of the PR label Jan 16, 2022
Co-authored-by: sgouezel <sebastien.gouezel@univ-rennes1.fr>
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dupuisf commented Jan 16, 2022

bors r+

bors bot pushed a commit that referenced this pull request Jan 16, 2022
…oid (#11457)

This PR defines `unitary R` for a star monoid `R` as the submonoid containing the elements that satisfy both `star U * U = 1` and `U * star U = 1`. We show basic properties (i.e. that this forms a group) and show that they
preserve the norm when `R` is a C* ring.

Note that this replaces `unitary_submonoid`, which only included the condition `star U * U = 1` -- see [the discussion](https://leanprover.zulipchat.com/#narrow/stream/116395-maths/topic/unitary.20submonoid) on Zulip.



Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
Co-authored-by: Frédéric Dupuis <31101893+dupuisf@users.noreply.github.com>
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bors bot commented Jan 16, 2022

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(algebra/star/unitary): (re)define unitary elements of a star monoid [Merged by Bors] - feat(algebra/star/unitary): (re)define unitary elements of a star monoid Jan 16, 2022
@bors bors bot closed this Jan 16, 2022
@bors bors bot deleted the dupuisf/unitary_def branch January 16, 2022 15:40
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5 participants