Bourbaki

Corollary 3

Tag 090L, permanent. Cite it as [Bourbaki, Tag 090L].

Integration, chapter V, § 2. Summable families of positive measures

— For every function f∈F+(X)f \in \mathscr{F}_+(X),

ν∗(f)≥∑α∈Aλα∗(f). \nu^*(f) \geq \sum_{\alpha \in A} \lambda_\alpha^*(f).

The inequality is obvious if ff is not ν\nu-moderated, because then ν∗(f)=+∞\nu^*(f) = +\infty (§1§ 1, No. 2, Prop. 7). If ff is ν\nu-moderated then ff is λα\lambda_\alpha-moderated for every α∈A\alpha \in A, because every ν\nu-integrable open set is λα\lambda_\alpha-integrable; the relation (4) then follows at once from (3) and from Prop. 7 of §1§ 1, No. 2.

It can happen that the two members of (4) are not equal, even when AA is countable and each of the λα\lambda_\alpha is a point measure (§1§ 1, Exer. 4 a)).

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

Cited by

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Cites

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Transcribed from the printed volume. Not translated.