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[Merged by Bors] - feat(measure_theory/group/geometry_of_numbers): Blichfeldt and Minkowski's theorems #2819

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@alexjbest alexjbest commented May 25, 2020

I had a go at Minkowski's convex body theorem and it works thanks to @urkud 's pidgeonhole for measurable spaces.


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@alexjbest alexjbest added help-wanted The author needs attention to resolve issues incomplete not-ready-to-merge WIP Work in progress labels May 25, 2020
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urkud commented May 26, 2020

Please split this into smaller PRs. E.g., I see that you have a prod.measure_space instance. This definitely can (and should) be a separate PR.

This way (a) some chunks will be merged before the whole diff is cleared; (b) people will be able to review parts of the PR that touch files they feel responsible for/comfortable with while not taking responsibility for other parts of your PR.

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Sorry I should have been more clear, the two large files in measure theory are from https://github.com/jtristan/stump-learnable if the authors are ok with it I will PR the relevant parts (separately), not all of it is needed for this application. But first I would like to know if defining the product measure via the monadic machinery they develop is the best way, or wether it is recommended to use a different approach to get the lebesgue measure on R^n .

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urkud commented May 26, 2020

stump-learnable is under the same Apache 2.0 license, so you may PR code from that repo without asking the authors as long as you preserve their copyrights. It's pretty clear to me that they're not going to submit PRs themselves.

@bryangingechen bryangingechen changed the title [WIP] feat(number_theory/geometry_of_numbers) Minkowski's theorem [WIP] feat(number_theory/geometry_of_numbers): Minkowski's theorem Jun 25, 2020
@alexjbest alexjbest added the please-adopt This PR/issue may have been abandoned by the original contributor. You are welcome to take it over. label Nov 1, 2020
@alexjbest alexjbest removed the help-wanted The author needs attention to resolve issues label Aug 8, 2021
@mathlib-dependent-issues-bot mathlib-dependent-issues-bot removed the blocked-by-other-PR This PR depends on another PR which is still in the queue. A bot manages this label via PR comment. label Jan 13, 2023
@mathlib-dependent-issues-bot mathlib-dependent-issues-bot added the blocked-by-other-PR This PR depends on another PR which is still in the queue. A bot manages this label via PR comment. label Feb 1, 2023
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xroblot commented Mar 30, 2023

I have committed a new proof of Minkowski's theorem (and Blichfeldt's theorem) that doesn't require a basis and thus doesn't rely anymore on #18343

@mathlib-dependent-issues-bot mathlib-dependent-issues-bot removed the blocked-by-other-PR This PR depends on another PR which is still in the queue. A bot manages this label via PR comment. label Mar 30, 2023
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xroblot commented Mar 30, 2023

The new version requires the hypothesis measurable_set T. As suggested by @YaelDillies, it would be nice to remove this hypothesis using the fact that T is convex using convex.null_measurable_set.

But, then it is necessary to prove that ((2⁻¹ : ℝ) • T) is also null_measurable_set for μ and there is no version of measurable_set.const_smul₀ for null_measurable_set.

I tried to prove the result but I did not succeed. In fact, there is measure_theory.null_measurable_set.smul that could be easily adapted to the case of group_with_zero but is requires that the measure is smul_invariant_measure and we certainly do not want that so I suspect this is not so easy to prove...

This is now fixed thanks to the help of Yaël.

open ennreal finite_dimensional measure_theory measure_theory.measure set
open_locale pointwise

variables {E L : Type*} [measurable_space E] {μ : measure E} {F s : set E}
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It feels weird to me to have F and s appear before all the typeclass arguments. Can you put these in the lemma statements instead?

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"typeclass arguments first" is a bit of a meaningless rule when you get to measure theory where there are many typeclasses some of which depend on non-typeclasses. I certainly won't enforce it here if it leads to duplicating variable declarations.

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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 Mar 31, 2023
bors bot pushed a commit that referenced this pull request Mar 31, 2023
…ski's theorems (#2819)

I had a go at Minkowski's convex body theorem and it works thanks to @urkud 's pidgeonhole for measurable spaces.



Co-authored-by: Yaël Dillies <yael.dillies@gmail.com>
Co-authored-by: Xavier-François Roblot <46200072+xroblot@users.noreply.github.com>
Co-authored-by: RemyDegenne <Remydegenne@gmail.com>
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bors bot commented Mar 31, 2023

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(measure_theory/group/geometry_of_numbers): Blichfeldt and Minkowski's theorems [Merged by Bors] - feat(measure_theory/group/geometry_of_numbers): Blichfeldt and Minkowski's theorems Mar 31, 2023
@bors bors bot closed this Mar 31, 2023
@bors bors bot deleted the minkowski branch March 31, 2023 22:20
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