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[Merged by Bors] - feat: cyclotomic fields are totally complex #10502

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@riccardobrasca riccardobrasca commented Feb 13, 2024

We prove that cyclotomic fields are totally complex.

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@riccardobrasca riccardobrasca added awaiting-review The author would like community review of the PR t-number-theory Number theory (also use t-algebra or t-analysis to specialize) t-algebra Algebra (groups, rings, fields etc) labels Feb 13, 2024
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@xroblot Do you see a quick way of proving that if finrank K = 1 then NrRealPlaces K = 1?

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xroblot commented Feb 14, 2024

@xroblot Do you see a quick way of proving that if finrank K = 1 then NrRealPlaces K = 1?

Well, I don't see a better way than to use NumberField.InfinitePlace.card_add_two_mul_card_eq_rank but I am sure you know that already.

Well, there might something possible using: IsUnramifiedAtInfinitePlaces_of_odd_finrank. It could be a bit faster... I am not sure.

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@xroblot Do you see a quick way of proving that if finrank K = 1 then NrRealPlaces K = 1?

Well, I don't see a better way than to use NumberField.InfinitePlace.card_add_two_mul_card_eq_rank but I am sure you know that already.

Well, there might something possible using: IsUnramifiedAtInfinitePlaces_of_odd_finrank. It could be a bit faster... I am not sure.

Ah, you're right! I didn't realize that NumberField.InfinitePlace.card_add_two_mul_card_eq_rank immediately gives a + 2*b = 1 so a = 1 and b = 0!

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I've generalized the fact that NrComplexPlaces K = φ n / 2 without the assumption that 2 < n (of course it holds for stupid reasons, but still).

@leanprover-community-mathlib4-bot leanprover-community-mathlib4-bot removed the merge-conflict The PR has a merge conflict with master, and needs manual merging. label Feb 19, 2024
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Besides the two golfing, LGTM.

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Thanks 🎉

bors merge

@github-actions github-actions bot added ready-to-merge This PR has been sent to bors. and removed awaiting-review The author would like community review of the PR labels Mar 1, 2024
mathlib-bors bot pushed a commit that referenced this pull request Mar 1, 2024
We prove that cyclotomic fields are totally complex.

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mathlib-bors bot commented Mar 1, 2024

Pull request successfully merged into master.

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@mathlib-bors mathlib-bors bot changed the title feat: cyclotomic fields are totally complex [Merged by Bors] - feat: cyclotomic fields are totally complex Mar 1, 2024
@mathlib-bors mathlib-bors bot closed this Mar 1, 2024
@mathlib-bors mathlib-bors bot deleted the RB/totally_complex branch March 1, 2024 15:31
riccardobrasca added a commit that referenced this pull request Mar 1, 2024
We prove that cyclotomic fields are totally complex.

From flt-regular.
mathlib-bors bot pushed a commit that referenced this pull request Mar 4, 2024
… = 3 or p = 5 (#10683)

We prove that the ring of integers of the p-th cyclotomic field is a PID if p = 3 or p = 5.

From flt-regular

- [x] depends on: #10492 
- [x] depends on: #10502
kbuzzard pushed a commit that referenced this pull request Mar 12, 2024
We prove that cyclotomic fields are totally complex.

From flt-regular.
kbuzzard pushed a commit that referenced this pull request Mar 12, 2024
… = 3 or p = 5 (#10683)

We prove that the ring of integers of the p-th cyclotomic field is a PID if p = 3 or p = 5.

From flt-regular

- [x] depends on: #10492 
- [x] depends on: #10502
dagurtomas pushed a commit that referenced this pull request Mar 22, 2024
We prove that cyclotomic fields are totally complex.

From flt-regular.
dagurtomas pushed a commit that referenced this pull request Mar 22, 2024
… = 3 or p = 5 (#10683)

We prove that the ring of integers of the p-th cyclotomic field is a PID if p = 3 or p = 5.

From flt-regular

- [x] depends on: #10492 
- [x] depends on: #10502
utensil pushed a commit that referenced this pull request Mar 26, 2024
We prove that cyclotomic fields are totally complex.

From flt-regular.
utensil pushed a commit that referenced this pull request Mar 26, 2024
… = 3 or p = 5 (#10683)

We prove that the ring of integers of the p-th cyclotomic field is a PID if p = 3 or p = 5.

From flt-regular

- [x] depends on: #10492 
- [x] depends on: #10502
Louddy pushed a commit that referenced this pull request Apr 15, 2024
We prove that cyclotomic fields are totally complex.

From flt-regular.
Louddy pushed a commit that referenced this pull request Apr 15, 2024
… = 3 or p = 5 (#10683)

We prove that the ring of integers of the p-th cyclotomic field is a PID if p = 3 or p = 5.

From flt-regular

- [x] depends on: #10492 
- [x] depends on: #10502
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5 participants