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[Merged by Bors] - feat(measure_theory/order/upper_lower): Order-connected sets in ℝⁿ are measurable #16976

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@YaelDillies YaelDillies commented Oct 14, 2022

Prove that the frontier of an order-connected set in ℝⁿ (with the -metric, but it doesn't actually matter) has measure zero.

As a corollary, antichains in ℝⁿ have measure zero.

Co-authored-by: @JasonKYi


This is a three lines remark in Reverse Kleitman Inequalities, Bollobas, Leader, Radcliffe, with no proof. So Jason, Bhavik and I came up with a proof using Lebesgue Density Theorem.

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@YaelDillies YaelDillies added awaiting-review The author would like community review of the PR blocked-by-other-PR This PR depends on another PR which is still in the queue. A bot manages this label via PR comment. t-order Order hierarchy t-measure-probability Measure theory / Probability theory labels Oct 14, 2022
@YaelDillies YaelDillies requested a review from a team as a code owner October 14, 2022 08:42
@github-actions github-actions bot added the modifies-synchronized-file This PR touches a files that has already been ported to mathlib4, and may need a synchronization PR. label Sep 19, 2023
@YaelDillies YaelDillies added not-too-late This PR was ready at the point mathlib3 was frozen: we will try to merge it and port it to mathlib4 and removed too-late This PR was ready too late for inclusion in mathlib3 labels Sep 19, 2023
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bors d+

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bors bot commented Oct 16, 2023

✌️ YaelDillies 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-bot-assistant leanprover-community-bot-assistant 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 Oct 16, 2023
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bors merge

bors bot pushed a commit that referenced this pull request Oct 16, 2023
…are measurable (#16976)

Prove that the frontier of an order-connected set in `ℝⁿ` (with the `∞`-metric, but it doesn't actually matter) has measure zero.

As a corollary, antichains in `ℝⁿ` have measure zero.

Co-authored-by: @JasonKYi
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@bors bors bot changed the title feat(measure_theory/order/upper_lower): Order-connected sets in ℝⁿ are measurable [Merged by Bors] - feat(measure_theory/order/upper_lower): Order-connected sets in ℝⁿ are measurable Oct 16, 2023
@bors bors bot closed this Oct 16, 2023
@bors bors bot deleted the ord_connected_measurable branch October 16, 2023 12:40
eric-wieser pushed a commit that referenced this pull request Oct 16, 2023
…are measurable (#16976)

Prove that the frontier of an order-connected set in `ℝⁿ` (with the `∞`-metric, but it doesn't actually matter) has measure zero.

As a corollary, antichains in `ℝⁿ` have measure zero.

Co-authored-by: @JasonKYi
mathlib-bors bot pushed a commit to leanprover-community/mathlib4 that referenced this pull request Feb 14, 2024
* Add `upperBounds_closure`, `lowerBounds_closure`, `bddAbove_closure`, `bddBelow_closure`.
* Add `IsAntichain.interior_eq_empty`.
* Generalize `nhds_left'_le_nhds_ne` and `nhds_right'_le_nhds_ne` to a `Preorder`.

Partly forward-ports leanprover-community/mathlib#16976
riccardobrasca pushed a commit to leanprover-community/mathlib4 that referenced this pull request Feb 18, 2024
* Add `upperBounds_closure`, `lowerBounds_closure`, `bddAbove_closure`, `bddBelow_closure`.
* Add `IsAntichain.interior_eq_empty`.
* Generalize `nhds_left'_le_nhds_ne` and `nhds_right'_le_nhds_ne` to a `Preorder`.

Partly forward-ports leanprover-community/mathlib#16976
dagurtomas pushed a commit to leanprover-community/mathlib4 that referenced this pull request Mar 22, 2024
* Add `upperBounds_closure`, `lowerBounds_closure`, `bddAbove_closure`, `bddBelow_closure`.
* Add `IsAntichain.interior_eq_empty`.
* Generalize `nhds_left'_le_nhds_ne` and `nhds_right'_le_nhds_ne` to a `Preorder`.

Partly forward-ports leanprover-community/mathlib#16976
YaelDillies added a commit to leanprover-community/mathlib4 that referenced this pull request Mar 23, 2024
mathlib-bors bot pushed a commit to leanprover-community/mathlib4 that referenced this pull request Mar 23, 2024
Partially forward-port leanprover-community/mathlib#16976

Also fix an unused argument that somehow made it to master, likely from #10661.
utensil pushed a commit to leanprover-community/mathlib4 that referenced this pull request Mar 26, 2024
Partially forward-port leanprover-community/mathlib#16976

Also fix an unused argument that somehow made it to master, likely from #10661.
Louddy pushed a commit to leanprover-community/mathlib4 that referenced this pull request Apr 15, 2024
Partially forward-port leanprover-community/mathlib#16976

Also fix an unused argument that somehow made it to master, likely from #10661.
atarnoam pushed a commit to leanprover-community/mathlib4 that referenced this pull request Apr 16, 2024
Partially forward-port leanprover-community/mathlib#16976

Also fix an unused argument that somehow made it to master, likely from #10661.
uniwuni pushed a commit to leanprover-community/mathlib4 that referenced this pull request Apr 19, 2024
Partially forward-port leanprover-community/mathlib#16976

Also fix an unused argument that somehow made it to master, likely from #10661.
callesonne pushed a commit to leanprover-community/mathlib4 that referenced this pull request Apr 22, 2024
Partially forward-port leanprover-community/mathlib#16976

Also fix an unused argument that somehow made it to master, likely from #10661.
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6 participants