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[Merged by Bors] - feat: the sigma-algebra generated by the constant indicator of a set is smaller than the one generated by the set #39753

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[Merged by Bors] - feat: the sigma-algebra generated by the constant indicator of a set is smaller than the one generated by the set #39753

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Automated addition of changes in Mathlib/MeasureTheory/MeasurableSpac…
EtienneC30 May 23, 2026
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6 changes: 6 additions & 0 deletions Mathlib/MeasureTheory/MeasurableSpace/MeasurablyGenerated.lean
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Expand Up @@ -42,6 +42,12 @@ lemma generateFrom_singleton_le {m : MeasurableSpace α} {s : Set α} (hs : Meas
MeasurableSpace.generateFrom {s} ≤ m :=
generateFrom_le (fun _ ht ↦ mem_singleton_iff.1 ht ▸ hs)

lemma comap_indicator_const_le_generateFrom_singleton {M : Type*} [Zero M] [MeasurableSpace M]
(s : Set α) (c : M) :
MeasurableSpace.comap (s.indicator (fun _ ↦ c)) inferInstance ≤
MeasurableSpace.generateFrom {s} :=
(measurable_const.indicator (measurableSet_generateFrom (by simp))).comap_le

end MeasurableSpace

namespace MeasureTheory
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