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[Merged by Bors] - feat(measure_theory/lp_space): add more API on Lp spaces #6042

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@sgouezel sgouezel commented Feb 4, 2021

Flesh out the file on L^p spaces, notably adding facts on the composition with Lipschitz functions. This makes it possible to define in one go the positive part of an L^p function, and its image under a continuous linear map.

The file ae_eq_fun.lean is split into two, to solve a temporary issue: this file defines a global emetric space instance (of L^1 type) on the space of function classes. This passes to subtypes, and clashes with the topology on L^p coming from the distance. This did not show up before as there were not enough topological statements on L^p, but I have been bitten by this when adding new results. For now, we move this part of ae_eq_fun.lean to another file which is not imported by lp_space.lean, to avoid the clash. This will be solved in a subsequent PR in which I will remove the global instance, and construct the integral based on the specialization of L^p to p = 1 instead of the ad hoc construction we have now (note that, currently, we have two different L^1 spaces in mathlib, denoted Lp E 1 μ and α →₁[μ] E -- I will remove the second one in a later PR).


The only file that is really changed in the PR is lp_space.lean, the rest is just the splitting of ae_eq_fun into two parts, without changing a line. In lp_space.lean, I have tried to uniformize things a little bit. In particular, p is now used consistently as an ennreal, and q as a real, as opposed to the previous situation where the roles of p and q were exchanged in the beginning of the file, for mainly historical reasons. This makes a big diff, but a lot of it is just this trivial substitution.

@sgouezel sgouezel added the awaiting-review The author would like community review of the PR label Feb 4, 2021
@github-actions github-actions bot added the merge-conflict Please `git merge origin/master` then a bot will remove this label. label Feb 5, 2021
@github-actions github-actions bot removed the merge-conflict Please `git merge origin/master` then a bot will remove this label. label Feb 5, 2021
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urkud commented Feb 7, 2021

In particular, p is now used consistently as an ennreal, and q as a real, as opposed to the previous situation where the roles of p and q were exchanged in the beginning of the file, for mainly historical reasons. This makes a big diff, but a lot of it is just this trivial substitution.

q is an ennreal in the definition of snorm.

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urkud commented Feb 7, 2021

Could you please open a PR from https://github.com/leanprover-community/mathlib/tree/split-ae-eq-fun (cherry-picked from your diff) and merge it right away?

@github-actions github-actions bot added the merge-conflict Please `git merge origin/master` then a bot will remove this label. label Feb 7, 2021
@github-actions github-actions bot removed the merge-conflict Please `git merge origin/master` then a bot will remove this label. label Feb 8, 2021
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urkud commented Feb 9, 2021

I golfed a few proofs, feel free to revert (some of) my changes or leave as is.
bors d+

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bors bot commented Feb 9, 2021

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

@bryangingechen bryangingechen added delegated The PR author may merge after reviewing final suggestions. and removed awaiting-review The author would like community review of the PR labels Feb 9, 2021
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sgouezel commented Feb 9, 2021

bors r+

@github-actions github-actions bot added the ready-to-merge All that is left is for bors to build and merge this PR. (Remember you need to say `bors r+`.) label Feb 9, 2021
bors bot pushed a commit that referenced this pull request Feb 10, 2021
Flesh out the file on `L^p` spaces, notably adding facts on the composition with Lipschitz functions. This makes it possible to define in one go the positive part of an `L^p` function, and its image under a continuous linear map.

The file `ae_eq_fun.lean` is split into two, to solve a temporary issue: this file defines a global emetric space instance (of `L^1` type) on the space of function classes. This passes to subtypes, and clashes with the topology on `L^p` coming from the distance. This did not show up before as there were not enough topological statements on `L^p`, but I have been bitten by this when adding new results. For now, we move this part of `ae_eq_fun.lean` to another file which is not imported by `lp_space.lean`, to avoid the clash. This will be solved in a subsequent PR in which I will remove the global instance, and construct the integral based on the specialization of `L^p` to `p = 1` instead of the ad hoc construction we have now (note that, currently, we have two different `L^1` spaces in mathlib, denoted `Lp E 1 μ` and `α →₁[μ] E` -- I will remove the second one in a later PR).



Co-authored-by: Yury G. Kudryashov <urkud@urkud.name>
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bors bot commented Feb 10, 2021

Pull request successfully merged into master.

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@bors bors bot changed the title feat(measure_theory/lp_space): add more API on Lp spaces [Merged by Bors] - feat(measure_theory/lp_space): add more API on Lp spaces Feb 10, 2021
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@bors bors bot deleted the more_Lp branch February 10, 2021 03:37
b-mehta pushed a commit that referenced this pull request Apr 2, 2021
b-mehta pushed a commit that referenced this pull request Apr 2, 2021
Flesh out the file on `L^p` spaces, notably adding facts on the composition with Lipschitz functions. This makes it possible to define in one go the positive part of an `L^p` function, and its image under a continuous linear map.

The file `ae_eq_fun.lean` is split into two, to solve a temporary issue: this file defines a global emetric space instance (of `L^1` type) on the space of function classes. This passes to subtypes, and clashes with the topology on `L^p` coming from the distance. This did not show up before as there were not enough topological statements on `L^p`, but I have been bitten by this when adding new results. For now, we move this part of `ae_eq_fun.lean` to another file which is not imported by `lp_space.lean`, to avoid the clash. This will be solved in a subsequent PR in which I will remove the global instance, and construct the integral based on the specialization of `L^p` to `p = 1` instead of the ad hoc construction we have now (note that, currently, we have two different `L^1` spaces in mathlib, denoted `Lp E 1 μ` and `α →₁[μ] E` -- I will remove the second one in a later PR).



Co-authored-by: Yury G. Kudryashov <urkud@urkud.name>
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