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[Merged by Bors] - feat(NumberTheory.NumberField.Units): add torsion subgroup#5748

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[Merged by Bors] - feat(NumberTheory.NumberField.Units): add torsion subgroup#5748
xroblot wants to merge 15 commits intomasterfrom
xfr-unit-torsion

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@xroblot xroblot commented Jul 6, 2023

We define the torsion subgroup of the units of a number field and prove some results about it, mostly: it is finite, cyclic and
an unit is torsion iff its value is 1 at all infinite places. Some results linking to rootsOfUnity are also proved.

This PR also includes a direct coercion from (𝓞 K)ˣ to K that is very convenient, although I am not sure it's done properly.


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@xroblot xroblot changed the title feat(NumberTheory.NumberField.Unit): add torsion subgroup feat(NumberTheory.NumberField.Units): add torsion subgroup Jul 6, 2023
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kim-em commented Jul 8, 2023

Please remember to add the label awaiting-review when this is ready for review. (Alternatively PRs that refactor files that were ported from mathlib3 should be labelled after-port.)

@xroblot xroblot added the WIP Work in progress label Jul 8, 2023
@xroblot xroblot added the t-number-theory Number theory (also use t-algebra or t-analysis to specialize) label Jul 16, 2023
@xroblot xroblot added awaiting-review and removed WIP Work in progress labels Jul 19, 2023
@xroblot xroblot added WIP Work in progress awaiting-review and removed awaiting-review WIP Work in progress labels Jul 24, 2023
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We probably want also the fact that the double coercion from (𝓞 K)ˣ to 𝓞 K to K is the same as the coercion from (𝓞 K)ˣ to K.

LGTM but I am not very familiar with coercions in Lean4. You can maybe ask on Zulip.

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xroblot commented Jul 29, 2023

We probably want also the fact that the double coercion from (𝓞 K)ˣ to 𝓞 K to K is the same as the coercion from (𝓞 K)ˣ to K.

LGTM but I am not very familiar with coercions in Lean4. You can maybe ask on Zulip.

As you suggested, I asked for some expert opinion on Zulip

@Vierkantor Vierkantor self-assigned this Jul 31, 2023
@Vierkantor Vierkantor added awaiting-author A reviewer has asked the author a question or requested changes. and removed awaiting-review labels Jul 31, 2023
@xroblot xroblot added awaiting-review and removed awaiting-author A reviewer has asked the author a question or requested changes. labels Aug 2, 2023
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Thanks!

bors d+

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bors bot commented Aug 2, 2023

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

@ghost ghost added delegated This pull request has been delegated to the PR author (or occasionally another non-maintainer). and removed awaiting-review labels Aug 2, 2023
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xroblot commented Aug 2, 2023

bors r+

bors bot pushed a commit that referenced this pull request Aug 2, 2023
We define the torsion subgroup of the units of a number field and prove some results about it, mostly: it is finite, cyclic and 
an unit is torsion iff its value is 1 at all infinite places. Some results linking to `rootsOfUnity` are also proved. 

This PR also includes a direct coercion from `(𝓞 K)ˣ` to `K` that is very convenient, although I am not sure it's done properly.
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@bors bors bot changed the title feat(NumberTheory.NumberField.Units): add torsion subgroup [Merged by Bors] - feat(NumberTheory.NumberField.Units): add torsion subgroup Aug 3, 2023
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@bors bors bot deleted the xfr-unit-torsion branch August 3, 2023 00:24
kim-em pushed a commit that referenced this pull request Aug 3, 2023
We define the torsion subgroup of the units of a number field and prove some results about it, mostly: it is finite, cyclic and 
an unit is torsion iff its value is 1 at all infinite places. Some results linking to `rootsOfUnity` are also proved. 

This PR also includes a direct coercion from `(𝓞 K)ˣ` to `K` that is very convenient, although I am not sure it's done properly.
kim-em pushed a commit that referenced this pull request Aug 3, 2023
We define the torsion subgroup of the units of a number field and prove some results about it, mostly: it is finite, cyclic and 
an unit is torsion iff its value is 1 at all infinite places. Some results linking to `rootsOfUnity` are also proved. 

This PR also includes a direct coercion from `(𝓞 K)ˣ` to `K` that is very convenient, although I am not sure it's done properly.
kim-em pushed a commit that referenced this pull request Aug 14, 2023
We define the torsion subgroup of the units of a number field and prove some results about it, mostly: it is finite, cyclic and 
an unit is torsion iff its value is 1 at all infinite places. Some results linking to `rootsOfUnity` are also proved. 

This PR also includes a direct coercion from `(𝓞 K)ˣ` to `K` that is very convenient, although I am not sure it's done properly.
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