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[Merged by Bors] - feat(probability_theory/independence): if a family of pi-systems is independent, then so are the generated measurable spaces #9387

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@RemyDegenne RemyDegenne commented Sep 25, 2021

The main result in this PR is Indep_sets.Indep: if π-systems are independent as sets of sets, then the
measurable space structures they generate are independent. We already had a version of this for two pi-systems instead of a family.

In order to prove this, and as preparation for a next PR about Kolmogorov's 0-1 law, a definition pi_Union_Inter is introduced to build a particular pi-system from a family of pi-systems.


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generate_from_mono is moved from measurable_space.lean to measurable_space_def.lean because I need it in the pi_system.lean file.

@RemyDegenne RemyDegenne added awaiting-review The author would like community review of the PR and removed WIP Work in progress awaiting-review The author would like community review of the PR merge-conflict Please `git merge origin/master` then a bot will remove this label. labels Jun 18, 2022
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bors d+
Thanks!

@@ -309,6 +308,119 @@ begin
exact indep_sets.indep_aux h2 hp2 hpm2 hyp ht ht2,
end

variables {α ι : Type*} {m0 : measurable_space α} {μ : measure α}

lemma pi_system_indep_insert {π : ι → set (set α)} {a : ι} {S : finset ι}
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The name of this lemma does not really match the symbols in the statement of the lemma.

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bors bot commented Jun 28, 2022

✌️ RemyDegenne 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 Jun 28, 2022
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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 Jun 28, 2022
bors bot pushed a commit that referenced this pull request Jun 28, 2022
…ndependent, then so are the generated measurable spaces (#9387)

The main result in this PR is `Indep_sets.Indep`: if π-systems are independent as sets of sets, then the
measurable space structures they generate are independent. We already had a version of this for two pi-systems instead of a family.

In order to prove this, and as preparation for a next PR about Kolmogorov's 0-1 law, a definition `pi_Union_Inter` is introduced to build a particular pi-system from a family of pi-systems.



Co-authored-by: Rémy Degenne <remydegenne@gmail.com>
Co-authored-by: sgouezel <sebastien.gouezel@univ-rennes1.fr>
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Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(probability_theory/independence): if a family of pi-systems is independent, then so are the generated measurable spaces [Merged by Bors] - feat(probability_theory/independence): if a family of pi-systems is independent, then so are the generated measurable spaces Jun 28, 2022
@bors bors bot closed this Jun 28, 2022
@bors bors bot deleted the independence_1 branch June 28, 2022 11:11
awainverse pushed a commit that referenced this pull request Jun 28, 2022
…ndependent, then so are the generated measurable spaces (#9387)

The main result in this PR is `Indep_sets.Indep`: if π-systems are independent as sets of sets, then the
measurable space structures they generate are independent. We already had a version of this for two pi-systems instead of a family.

In order to prove this, and as preparation for a next PR about Kolmogorov's 0-1 law, a definition `pi_Union_Inter` is introduced to build a particular pi-system from a family of pi-systems.



Co-authored-by: Rémy Degenne <remydegenne@gmail.com>
Co-authored-by: sgouezel <sebastien.gouezel@univ-rennes1.fr>
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