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[Merged by Bors] - feat: prove the Gagliardo-Nirenberg-Sobolev inequality #14165

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@fpvandoorn fpvandoorn commented Jun 26, 2024

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github-actions bot commented Jun 26, 2024

PR summary 809a3c5646

Import changes

No significant changes to the import graph


Declarations diff

+ T
+ T_empty
+ T_insert_le_T_lmarginal_singleton
+ T_lmarginal_antitone
+ T_univ
+ argument
+ lintegral_mul_prod_lintegral_pow_le
+ lintegral_pow_le_pow_lintegral_fderiv
+ lintegral_pow_le_pow_lintegral_fderiv_aux
+ lintegral_prod_lintegral_pow_le
+ snormLESNormFDerivOfEqInnerConst
+ snorm_le_snorm_fderiv
+ snorm_le_snorm_fderiv_of_eq
+ snorm_le_snorm_fderiv_of_eq_inner
+ snorm_le_snorm_fderiv_of_le
+ snorm_le_snorm_fderiv_one
+ snorm_restrict_eq

You can run this locally as follows
## summary with just the declaration names:
./scripts/no_lost_declarations.sh short <optional_commit>

## more verbose report:
./scripts/no_lost_declarations.sh <optional_commit>

@leanprover-community-mathlib4-bot leanprover-community-mathlib4-bot added the blocked-by-other-PR This PR depends on another PR to Mathlib (this label is automatically managed by a bot) label Jun 26, 2024
@leanprover-community-mathlib4-bot leanprover-community-mathlib4-bot removed the blocked-by-other-PR This PR depends on another PR to Mathlib (this label is automatically managed by a bot) label Jun 26, 2024
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@@ -672,6 +672,13 @@ theorem memℒp_indicator_iff_restrict (hs : MeasurableSet s) :
simp [Memℒp, aestronglyMeasurable_indicator_iff hs, snorm_indicator_eq_snorm_restrict hs]
#align measure_theory.mem_ℒp_indicator_iff_restrict MeasureTheory.memℒp_indicator_iff_restrict

/-- For a function `f` with support in `s`, the Lᵖ norms of `f` with respect to `μ` and
`μ.restrict s` are the same. -/
theorem snorm_restrict_eq {s : Set α} (hs : MeasurableSet s) (hsf : f.support ⊆ s) :
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hs shouldn't be needed: otherwise, use the measurable hull of s instead. Since it contains s, it will also satisfy hsf

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I also thought that, but I wasn't sure how to get snorm f p (μ.restrict s) = snorm f p (μ.restrict (toMeasurable μ s))

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I can replace (hs : MeasurableSet s) by [SFinite μ]. Do you think that is better? Both are true in my application.

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I replaced the lemma, and this is actually nicer. I didn't realize we had to put some effort in making the set measurable when we applied it, so this is a nice simplification.

This does add a small amount of imports to the file LpSpace.

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I have a proof removing the SFinite assumption, but I will first wait for #14260 to be merged, to avoid introducing new lemmas with a wrong name.

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See #14289

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It feels weird to have this in the MeasureTheory folder; this is firmly a statement in analysis, just like all Sobolev spaces theory. Maybe create a folder Analysis/FunctionalSpaces and put it there?

@@ -672,6 +673,15 @@ theorem memℒp_indicator_iff_restrict (hs : MeasurableSet s) :
simp [Memℒp, aestronglyMeasurable_indicator_iff hs, snorm_indicator_eq_snorm_restrict hs]
#align measure_theory.mem_ℒp_indicator_iff_restrict MeasureTheory.memℒp_indicator_iff_restrict

/-- For a function `f` with support in `s`, the Lᵖ norms of `f` with respect to `μ` and
`μ.restrict s` are the same. -/
theorem snorm_restrict_eq [SFinite μ] {s : Set α} (hsf : f.support ⊆ s) :
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In fact I think it's possible to get rid also of the SFinite condition, but I'll do that after this PR is merged.


/-! ## The Gagliardo-Nirenberg-Sobolev inequality -/

variable {F : Type*} [NormedAddCommGroup F] [NormedSpace ℝ F] [CompleteSpace F]
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The completeness assumption here is probably not necessary, but removing this can definitely wait for another PR.

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Done in #14262

@sgouezel sgouezel added awaiting-author A reviewer has asked the author a question or requested changes and removed awaiting-review labels Jun 28, 2024
@fpvandoorn fpvandoorn added awaiting-review and removed awaiting-author A reviewer has asked the author a question or requested changes labels Jun 28, 2024
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Thanks for your quick reviews!
I don't see how to quickly do the 2 suggested generalizations, so let's leave them for a later PR.
I incorporated your last suggestion, reformulated docstrings with this change, and added a paragraph in the module doc explaining this.

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bors d+
Thanks!

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mathlib-bors bot commented Jun 28, 2024

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

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bors merge

@github-actions github-actions bot added the ready-to-merge This PR has been sent to bors. label Jun 28, 2024
mathlib-bors bot pushed a commit that referenced this pull request Jun 28, 2024
* From the Sobolev inequality project

Co-authored-by: Heather Macbeth [email protected]
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mathlib-bors bot commented Jun 28, 2024

Pull request successfully merged into master.

Build succeeded:

@mathlib-bors mathlib-bors bot changed the title feat: prove the Gagliardo-Nirenberg-Sobolev inequality [Merged by Bors] - feat: prove the Gagliardo-Nirenberg-Sobolev inequality Jun 28, 2024
@mathlib-bors mathlib-bors bot closed this Jun 28, 2024
@mathlib-bors mathlib-bors bot deleted the sobolevinequality branch June 28, 2024 22:35
mathlib-bors bot pushed a commit that referenced this pull request Jun 29, 2024
* Forgot to incorporate 1 review comment from #14165
dagurtomas pushed a commit that referenced this pull request Jul 2, 2024
* From the Sobolev inequality project

Co-authored-by: Heather Macbeth [email protected]
dagurtomas pushed a commit that referenced this pull request Jul 2, 2024
* Forgot to incorporate 1 review comment from #14165
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4 participants