Bourbaki

Corollary 2

Tag 08R4, permanent. Cite it as [Bourbaki, Tag 08R4].

Integration, chapter IV, § 3. LP spaces

— Let E\mathscr{E} be a dense subset of LFp\mathscr{L}_F^p. For every function f∈LFpf \in \mathscr{L}_F^p, there exists a sequence (gn)(g_n) of functions in E\mathscr{E} having the following properties:

1° the sequence (gn)(g_n) converges in mean of order pp to ff; 2° for almost every x∈Xx \in X, the sequence (gn(x))(g_n(x)) converges to f(x)f(x).

For, since the space LFp\mathscr{L}_F^p is metrizable, there exists a Cauchy sequence (fn)(f_n) in LFp\mathscr{L}_F^p consisting of functions in E\mathscr{E} and convergent in mean of order pp to ff (GT, IX, §2, No. 6, Prop. 8); it suffices to apply Th. 3 to this sequence.

Cor. 2 is applicable in particular to the case where E\mathscr{E} is taken to be the space KF\mathscr{K}_F of continuous functions with compact support.

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.