Bourbaki

Corollary

Tag 092V, permanent. Cite it as [Bourbaki, Tag 092V].

Integration, chapter V, § 5. Measures defined by numerical densities

— Let (gα)(g_\alpha) be a sequence of locally μ\mu-integrable numerical functions, such that the sequence of measures gn⋅μg_n \cdot \mu is increasing. In order that this sequence have an upper bound in the ordered vector space M(T)\mathscr{M}(T) of real measures on T, it is necessary and sufficient that the function g=sup⁡gng = \sup g_n be locally μ\mu-integrable; the supremum in M(T)\mathscr{M}(T) of the sequence (gn⋅μ)(g_n \cdot \mu) is then the measure g⋅μg \cdot \mu.

It suffices to apply Prop. 6 to the functions (positive locally almost everywhere) gn′=gn+1−gng'_n = g_{n+1} - g_n.

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

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Transcribed from the printed volume. Not translated.