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[Merged by Bors] - feat: construct Haar measure in locally compact non-Hausdorff groups #9746

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The construction we have is given in T2 spaces, but it works in non-Hausdorff spaces modulo a few modifications.

For this, we introduce an ad hoc class T2OrLocallyCompactRegularSpace, which is just enough to unify the arguments, as a replacement for the class ClosableCompactSubsetOpenSpace (which is not strong enough). In the file Separation.lean, we move some material that was only available on T2 spaces to this new class.

The construction is needed for a forthcoming improvement of uniqueness results for Haar measures, based on https://mathoverflow.net/questions/456670/uniqueness-of-left-invariant-borel-probability-measure-on-compact-groups.


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@sgouezel sgouezel added awaiting-review The author would like community review of the PR t-measure-probability Measure theory / Probability theory labels Jan 14, 2024
@sgouezel sgouezel changed the title feat: construct Haar measure in non-Hausdorff spaces feat: construct Haar measure in locally compact non-Hausdorff groups Jan 14, 2024
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Thanks!
bors d+

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mathlib-bors bot commented Jan 18, 2024

✌️ 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.

@leanprover-community-mathlib4-bot leanprover-community-mathlib4-bot added delegated and removed awaiting-review The author would like community review of the PR labels Jan 18, 2024
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bors r+

@github-actions github-actions bot added the ready-to-merge This PR has been sent to bors. label Jan 18, 2024
mathlib-bors bot pushed a commit that referenced this pull request Jan 18, 2024
…9746)

The construction we have is given in T2 spaces, but it works in non-Hausdorff spaces modulo a few modifications. 

For this, we introduce an ad hoc class `T2OrLocallyCompactRegularSpace`, which is just enough to unify the arguments, as a replacement for the class `ClosableCompactSubsetOpenSpace` (which is not strong enough). In the file `Separation.lean`, we move some material that was only available on T2 spaces to this new class.

The construction is needed for a forthcoming improvement of uniqueness results for Haar measures, based on https://mathoverflow.net/questions/456670/uniqueness-of-left-invariant-borel-probability-measure-on-compact-groups.
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mathlib-bors bot commented Jan 18, 2024

Pull request successfully merged into master.

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@mathlib-bors mathlib-bors bot changed the title feat: construct Haar measure in locally compact non-Hausdorff groups [Merged by Bors] - feat: construct Haar measure in locally compact non-Hausdorff groups Jan 18, 2024
@mathlib-bors mathlib-bors bot closed this Jan 18, 2024
@mathlib-bors mathlib-bors bot deleted the SG_haar_unique2 branch January 18, 2024 10:31
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3 participants