Bourbaki

Example

Tag 0793, permanent. Cite it as [Bourbaki, Tag 0793].

Topological Vector Spaces, I, p. 12, § 2. Linear varieties in a topological vector space

— 1) In the normed space C(I;C)\mathscr{C}(I; \mathbf{C}) (on the field C\mathbf{C}) of functions, continuous on I={0,1}I = \{0, 1\}, with values in C\mathbf{C}, the restrictions to II of the functions xn (n∈N)x^n \ (n \in \mathbf{N}) form a total set, by the Weierstrass-Stone theorem (GT, X, § 4.2, th. 3). Similarly, the restrictions to II of the functions e2nπix (n∈Z)e^{2n\pi ix} \ (n \in \mathbf{Z}) form a total set (GT, X, § 4.4, prop. 8), in the subspace PP of C(I,C)\mathscr{C}(I, \mathbf{C}) formed of functions such that f(0)=f(1)f(0) = f(1).

2) Every absorbent set in a topological vector space EE over a non-discrete valued division ring (and in particular every neighbourhood of 0 in EE) is a total set since it generates EE (I, p. 7). Thus a linear variety that is not dense in EE is necessarily a nowhere dense set in EE (GT, IX, § 5.1) since its closure cannot contain an interior point.

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

Cited by

Nothing.

Cites

  • IX, § 5 not yet on this site
  • X, § 4 not yet on this site
Transcribed from the printed volume. Not translated.