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feat: Dieudonné measure on a well-order#39746

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feat: Dieudonné measure on a well-order#39746
vihdzp wants to merge 53 commits into
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vihdzp:dieudonne

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@vihdzp vihdzp commented May 23, 2026

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Given a well-order of uncountable cofinality, we can define a measurable space, consisting of sets which either contain or entirely omit a club set. On this space, the indicator function of stationary sets is a measure, known as the Dieudonné measure. It is a zero-one measure, which is nevertheless not a Dirac measure; it in fact has empty support.


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PR summary 64caf25786

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference
Mathlib.MeasureTheory.Constructions.Dieudonne (new file) 1624

Declarations diff

+ DirSupClosed.Ici
+ DirSupClosed.Iic
+ DirSupClosed.Ioi
+ DirSupClosedOn.Ici
+ DirSupClosedOn.Iic
+ DirSupClosedOn.Ioi
+ DirSupInacc.Iic
+ DirSupInacc.Ioi
+ DirSupInaccOn.Iic
+ DirSupInaccOn.Ioi
+ Ici_inter
+ Ioi_inter
+ IsClub.isStationary
+ IsCofinal.Ici
+ IsCofinal.Ioi
+ IsCofinal.inter_of_isUpperSet_left
+ IsCofinal.inter_of_isUpperSet_right
+ IsCofinal.nonempty
+ IsStationary
+ IsStationary.isCofinal
+ IsStationary.mono
+ IsStationary.nonempty
+ IsStationary.of_not_isCofinal_compl
+ IsStationary.singleton_top
+ IsStationary.univ
+ IsUpperSet.isCofinal
+ _root_.IsMax.isClub_singleton
+ _root_.isClub_Ici
+ _root_.isClub_Ioi
+ _root_.isClub_empty_iff
+ _root_.isUpperSet_Ici
+ _root_.isUpperSet_Ioi
+ coe_mk
+ exists_isClub_subset
+ iInter_of_countable
+ instance : IsZeroOneMeasure (α := α) measure
+ instance : MeasurableSingletonClass α
+ instance [NoMaxOrder α] : NoAtoms (α := α) measure
+ instance [Nonempty α] : IsProbabilityMeasure (α := α) measure
+ inter_Ici
+ inter_Ioi
+ isStationary_iUnion_iff
+ isStationary_iUnion_iff_of_cof_le_one
+ isStationary_iUnion_iff_of_countable
+ isStationary_iUnion_iff_of_orderTop
+ isStationary_iff_top_mem
+ isStationary_sUnion_iff
+ isStationary_sUnion_iff_of_cof_le_one
+ isStationary_sUnion_iff_of_countable
+ isStationary_sUnion_iff_of_orderTop
+ isStationary_singleton_iff
+ isStationary_union_iff
+ isStationary_univ_iff
+ measurableSet_def
+ measurableSet_of_isClub
+ measurableSet_of_not_isStationary
+ measurableSet_of_orderTop
+ measure
+ measure_eq_dirac
+ measure_eq_one_iff
+ measure_eq_zero_iff
+ measure_of_isClub
+ measure_of_isStationary
+ measure_of_not_isCofinal
+ measure_of_not_isStationary
+ nonempty
+ not_isCofinal_Iio
+ not_isStationary_empty
+ not_isStationary_iff
+ not_isStationary_of_isEmpty
+ not_isStationary_singleton
+ sInter_of_countable
+ singleton_top
+ support_measure
- isUpperSet_Ici
- isUpperSet_Ioi

You can run this locally as follows
## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.


No changes to strong technical debt.
No changes to weak technical debt.

@vihdzp vihdzp added t-set-theory Set theory t-measure-probability Measure theory / Probability theory labels May 23, 2026
@mathlib-dependent-issues mathlib-dependent-issues Bot added the blocked-by-other-PR This PR depends on another PR (this label is automatically managed by a bot) label May 23, 2026
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mathlib-dependent-issues Bot commented May 23, 2026

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This pull request has conflicts, please merge master and resolve them.

@mathlib-merge-conflicts mathlib-merge-conflicts 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 Jun 23, 2026
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