Bourbaki

Proposition 11

Tag 07I2, permanent. Cite it as [Bourbaki, Tag 07I2].

Topological Vector Spaces, II, p. 52, § 6. Weak topologies

Let EE be a Hausdorff weak space, and CC be a proper convex cone with vertex 0 in EE and which is complete in the uniform structure induced by that of EE.

Then there exists a set I and a continuous linear mapping u of E in the product space RI\mathbf{R}^I with the following properties:

a) u is an isomorphism of C on u(C)u(C) for the uniform structures induced respectively by those of E and of RI\mathbf{R}^I.

b) We have u(C)⊂R+Iu(C) \subset \mathbf{R}_+^I.

Further, if the uniform structure induced on C by that of E is metrisable, then we can take I=NI = \mathbf{N}.

Let (fi)i∈I(f_i)_{i \in I} be a family of continuous linear forms in E such that the finite sums of pseudometrics of the form (x,y)↦∣fi(x−y)∣(x, y) \mapsto |f_i(x - y)| on C×CC \times C define the uniform structure of C. (If the structure is metrisable we can take I=NI = \mathbf{N}.) By lemma 1 we can suppose further that each of the fif_i is positive in C. Let u be the linear mapping x↦(fi(x))i∈Ix \mapsto (f_i(x))_{i \in I} of E in RI\mathbf{R}^I. It is clear that u is continuous and that u(C)⊂R+Iu(C) \subset \mathbf{R}_+^I. The restriction u∣Cu|C is a uniformly continuous mapping that is surjective from C on u(C)u(C). Further if x,yx, y in C are such that fi(x)=fi(y)f_i(x) = f_i(y) for all i∈Ii \in I, then x=yx = y since the uniform structure of C is Hausdorff; therefore u∣Cu|C is bijective. Finally, if W is an entourage of the uniform structure of C, then there exists a finite set J of I and a number ε>0\varepsilon > 0 such that the relations ∣fi(x)−fi(y)∣≤ε|f_i(x) - f_i(y)| \leq \varepsilon for i∈Ji \in J imply (x,y)∈W(x, y) \in W; therefore u∣Cu|C is an isomorphism of C on u(C)u(C) for the uniform structures being considered.

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.