Bourbaki

Definition 1

Tag 09S6, permanent. Cite it as [Bourbaki, Tag 09S6].

Integration, IX, p. 73, § 6. Promeasures and measures on a locally convex space

Let EE be a locally convex space. One calls promeasure on EE every inverse system(1)^{(1)} of measures (§ 4, No. 2, Def. 1) on the inverse system of finite-dimensional quotients of EE.

In other words, a promeasure μ\mu on EE is a family (μV)V∈F(E)(\mu_V)_{V \in \mathscr{F}(E)}, where μV\mu_V is a bounded (positive) measure on the finite-dimensional space E/VE/V, and where μV=pVW(μW)\mu_V = p_{VW}(\mu_W) when V⊃WV \supset W. All of the measures μV\mu_V have the same total mass, which is called the total mass of the promeasure μ\mu.

For a subspace VV of EE to belong to F(E)\mathscr{F}(E), it is necessary and sufficient that there exist a finite number of elements x1′,…,xn′x'_1, \ldots, x'_n of E′E' such that VV consists of the x∈Ex \in E satisfying ⟨x,xi′⟩=0\langle x, x'_i \rangle = 0 for 1≤i≤n1 \leq i \leq n (TVS, II, § 6, No. 3, Cor. 2 of Th. 1 and No. 5, Cor. 2 of Prop. 7). Moreover, on a finite-dimensional vector space there exists one and only one Hausdorff topological vector space topology (TVS, I, § 2, No. 3, Th. 2). Consequently, the concept of promeasure on EE depends only on the dual E′E' of EE.

Let λ\lambda be a bounded measure on EE. For every V∈F(E)V \in \mathscr{F}(E), let us denote by λ~V\widetilde{\lambda}_V the image of λ\lambda under the canonical mapping pVp_V of EE onto E/VE/V. One has pV=pVW∘pWp_V = p_{VW} \circ p_W for any two elements VV and WW of F(E)\mathscr{F}(E) such that V⊃WV \supset W; consequently, the family λ~=(λ~V)V∈F(E)\widetilde{\lambda} = (\widetilde{\lambda}_V)_{V \in \mathscr{F}(E)} is a promeasure on EE. We shall say that λ~\widetilde{\lambda} is the promeasure associated with the measure λ\lambda. One sees immediately that λ\lambda and λ~\widetilde{\lambda} have the same total mass.

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.