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[Merged by Bors] - feat(combinatorics/additive/salem_spencer): The sphere does not contain arithmetic progressions #13259

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Prove that the frontier of a strictly convex closed set is Salem-Spencer. For this we need

  • simple lemmas about same_ray. This involves renaming same_ray.exists_right_eq_smul/same_ray.exists_left_eq_smul to same_ray.exists_nonneg_left/same_ray.exists_nonneg_right.
  • that the norm in a real normed space is injective on rays.
  • that the midpoint of two points of equal norm has smaller norm, in a strictly convex space

This is a very nice stress test of the library, because the end result is combinatorics but everything that leads to it is functional analysis.

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@YaelDillies YaelDillies added the awaiting-review The author would like community review of the PR label Apr 8, 2022
@YaelDillies YaelDillies requested a review from urkud April 8, 2022 23:52
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Thanks 🎉

bors merge

@leanprover-community-bot-assistant leanprover-community-bot-assistant 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 Apr 9, 2022
bors bot pushed a commit that referenced this pull request Apr 9, 2022
…in arithmetic progressions (#13259)

Prove that the frontier of a strictly convex closed set is Salem-Spencer. For this we need
* simple lemmas about `same_ray`. This involves renaming `same_ray.exists_right_eq_smul`/`same_ray.exists_left_eq_smul` to `same_ray.exists_nonneg_left`/`same_ray.exists_nonneg_right`.
* that the norm in a real normed space is injective on rays.
* that the midpoint of two points of equal norm has smaller norm, in a strictly convex space
@bors
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bors bot commented Apr 9, 2022

Build failed (retrying...):

bors bot pushed a commit that referenced this pull request Apr 9, 2022
…in arithmetic progressions (#13259)

Prove that the frontier of a strictly convex closed set is Salem-Spencer. For this we need
* simple lemmas about `same_ray`. This involves renaming `same_ray.exists_right_eq_smul`/`same_ray.exists_left_eq_smul` to `same_ray.exists_nonneg_left`/`same_ray.exists_nonneg_right`.
* that the norm in a real normed space is injective on rays.
* that the midpoint of two points of equal norm has smaller norm, in a strictly convex space
@bors
Copy link

bors bot commented Apr 9, 2022

Build failed (retrying...):

bors bot pushed a commit that referenced this pull request Apr 9, 2022
…in arithmetic progressions (#13259)

Prove that the frontier of a strictly convex closed set is Salem-Spencer. For this we need
* simple lemmas about `same_ray`. This involves renaming `same_ray.exists_right_eq_smul`/`same_ray.exists_left_eq_smul` to `same_ray.exists_nonneg_left`/`same_ray.exists_nonneg_right`.
* that the norm in a real normed space is injective on rays.
* that the midpoint of two points of equal norm has smaller norm, in a strictly convex space
@bors
Copy link

bors bot commented Apr 9, 2022

Build failed (retrying...):

bors bot pushed a commit that referenced this pull request Apr 9, 2022
…in arithmetic progressions (#13259)

Prove that the frontier of a strictly convex closed set is Salem-Spencer. For this we need
* simple lemmas about `same_ray`. This involves renaming `same_ray.exists_right_eq_smul`/`same_ray.exists_left_eq_smul` to `same_ray.exists_nonneg_left`/`same_ray.exists_nonneg_right`.
* that the norm in a real normed space is injective on rays.
* that the midpoint of two points of equal norm has smaller norm, in a strictly convex space
@bors
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bors bot commented Apr 9, 2022

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(combinatorics/additive/salem_spencer): The sphere does not contain arithmetic progressions [Merged by Bors] - feat(combinatorics/additive/salem_spencer): The sphere does not contain arithmetic progressions Apr 9, 2022
@bors bors bot closed this Apr 9, 2022
@bors bors bot deleted the salem_spencer_sphere branch April 9, 2022 23:53
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3 participants