Bourbaki

Remark

Tag 09A5, permanent. Cite it as [Bourbaki, Tag 09A5].

Integration, chapter VI, § 2. Vectorial measures . "

— 1) For a linear mapping m of K(T)\mathscr{K}(T) into F to be a vectorial measure, it is necessary and sufficient that, for every compact subset K of T, the image under m of the unit ball ∥f∥≤1\|f\| \leq 1 of K(T,K)\mathscr{K}(T, K) be bounded in F. The notion of vectorial measure with values in F is therefore the same for all the Hausdorff locally convex topologies on F that admit the same bounded sets, and in particular for all the topologies compatible with the duality between F and F' (TVS, IV, §1, No. 1, Prop. 1).

2) Let T1T_1 be a locally compact space, F1F_1 a Hausdorff locally convex space over R\mathbf{R}, u a continuous linear mapping of K(T1)\mathscr{K}(T_1) into K(T)\mathscr{K}(T), and v a continuous linear mapping of F into F1F_1. If m is a vectorial measure on T with values in F, then v∘m∘uv \circ m \circ u is a vectorial measure on T1T_1 with values in F1F_1. In particular, if g is a continuous, finite numerical function on T, then f↦m(gf)f \mapsto m(gf) is a vectorial measure on T with values in F, which is denoted g⋅mg \cdot m; if h is a second continuous, finite numerical function on T, then g⋅(h⋅m)=(gh)⋅mg \cdot (h \cdot m) = (gh) \cdot m.

3) Since the space K(T)\mathscr{K}(T) is the direct limit of the Banach spaces K(T,K)\mathscr{K}(T, K), and is in particular barreled (TVS, III, §4, No. 1, Cor. of Prop. 2 and Cor. 3 of Prop. 3), in order that a linear mapping m of K(T)\mathscr{K}(T) into F be a vectorial measure, it is necessary and sufficient that, for every z′∈F′z' \in F', z′∘mz' \circ m be a scalar measure on T (TVS, II, §6, No. 4, Prop. 5 and IV, §1, No. 3, Prop. 7).

4) In view of Remark 1, Prop. 1 of Ch. III, §2, No. 1 and its proof are again valid for vectorial measures. One can therefore define the support of a vectorial measure m on T to be the complement of the largest open set U⊂TU \subset T such that the restriction of m to U is zero.

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

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Cites

Transcribed from the printed volume. Not translated.