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[Merged by Bors] - feat: Prove that the measure equivalence between EuclideanSpace ℝ ι and ι → ℝ is volume preserving #7037

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@xroblot xroblot commented Sep 8, 2023

We prove that the two MeasureSpace structures on $\mathbb{R}^\iota$, the one coming from its identification with ι→ ℝ and the one coming from EuclideanSpace ℝ ι, agree in the sense that the measure equivalence between the two corresponding volumes is measure preserving.

Co-authored-by: Eric Wieser [email protected]


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@xroblot xroblot added the t-measure-probability Measure theory / Probability theory label Sep 8, 2023
@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 Sep 8, 2023
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I'll try to find some time to review the dependency one more time in the next few days. Thanks for getting this over the finish line!

Mathlib/Analysis/InnerProductSpace/PiL2.lean Outdated Show resolved Hide resolved
bors bot pushed a commit that referenced this pull request Sep 12, 2023
We prove some lemmas that will be useful in following PRs #6832 and #7037, mainly:
```lean
theorem Basis.addHaar_eq {b : Basis ι ℝ E} {b' : Basis ι' ℝ E} :
     b.addHaar = b'.addHaar ↔ b.addHaar b'.parallelepiped = 1

theorem Basis.parallelepiped_eq_map (b : Basis ι ℝ E) :
     b.parallelepiped = (TopologicalSpace.PositiveCompacts.piIcc01 ι).map b.equivFun.symm
       b.equivFunL.symm.continuous

theorem Basis.addHaar_map (b : Basis ι ℝ E) (f : E ≃L[ℝ] F) :
    map f b.addHaar = (b.map f.toLinearEquiv).addHaar
```

Co-authored-by: Eric Wieser <[email protected]>
bors bot pushed a commit that referenced this pull request Sep 12, 2023
We prove some lemmas that will be useful in following PRs #6832 and #7037, mainly:
```lean
theorem Basis.addHaar_eq {b : Basis ι ℝ E} {b' : Basis ι' ℝ E} :
     b.addHaar = b'.addHaar ↔ b.addHaar b'.parallelepiped = 1

theorem Basis.parallelepiped_eq_map (b : Basis ι ℝ E) :
     b.parallelepiped = (TopologicalSpace.PositiveCompacts.piIcc01 ι).map b.equivFun.symm
       b.equivFunL.symm.continuous

theorem Basis.addHaar_map (b : Basis ι ℝ E) (f : E ≃L[ℝ] F) :
    map f b.addHaar = (b.map f.toLinearEquiv).addHaar
```

Co-authored-by: Eric Wieser <[email protected]>
@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 Sep 12, 2023
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@leanprover-community-mathlib4-bot leanprover-community-mathlib4-bot added the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Sep 12, 2023
@leanprover-community-mathlib4-bot leanprover-community-mathlib4-bot removed the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Sep 12, 2023
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bors d+

Thanks! I added a few shortcut lemmas; let me know if you agree with them.

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bors bot commented Sep 13, 2023

✌️ xroblot 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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xroblot commented Sep 13, 2023

LGTM. Thanks!

bors r+

bors bot pushed a commit that referenced this pull request Sep 13, 2023
…nd ι → ℝ is volume preserving (#7037)

We prove that the two `MeasureSpace` structures on $\mathbb{R}^\iota$, the one coming from its identification with `ι→ ℝ` and the one coming from `EuclideanSpace ℝ ι`, agree in the sense that the measure equivalence between the two corresponding volumes is measure preserving. 


Co-authored-by: Eric Wieser <[email protected]>



Co-authored-by: Eric Wieser <[email protected]>
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@bors bors bot changed the title feat: Prove that the measure equivalence between EuclideanSpace ℝ ι and ι → ℝ is volume preserving [Merged by Bors] - feat: Prove that the measure equivalence between EuclideanSpace ℝ ι and ι → ℝ is volume preserving Sep 13, 2023
@bors bors bot closed this Sep 13, 2023
@bors bors bot deleted the xfr-euclidean_preserve_measure branch September 13, 2023 11:46
kodyvajjha pushed a commit that referenced this pull request Sep 22, 2023
We prove some lemmas that will be useful in following PRs #6832 and #7037, mainly:
```lean
theorem Basis.addHaar_eq {b : Basis ι ℝ E} {b' : Basis ι' ℝ E} :
     b.addHaar = b'.addHaar ↔ b.addHaar b'.parallelepiped = 1

theorem Basis.parallelepiped_eq_map (b : Basis ι ℝ E) :
     b.parallelepiped = (TopologicalSpace.PositiveCompacts.piIcc01 ι).map b.equivFun.symm
       b.equivFunL.symm.continuous

theorem Basis.addHaar_map (b : Basis ι ℝ E) (f : E ≃L[ℝ] F) :
    map f b.addHaar = (b.map f.toLinearEquiv).addHaar
```

Co-authored-by: Eric Wieser <[email protected]>
kodyvajjha pushed a commit that referenced this pull request Sep 22, 2023
…nd ι → ℝ is volume preserving (#7037)

We prove that the two `MeasureSpace` structures on $\mathbb{R}^\iota$, the one coming from its identification with `ι→ ℝ` and the one coming from `EuclideanSpace ℝ ι`, agree in the sense that the measure equivalence between the two corresponding volumes is measure preserving. 


Co-authored-by: Eric Wieser <[email protected]>



Co-authored-by: Eric Wieser <[email protected]>
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