Bourbaki

Remark 2

Tag 0CBK, permanent. Cite it as [Bourbaki, Tag 0CBK].

General Topology, chapter X, § 1. The uniformity of $\mathscr{G}$-convergence

A filter on C(X;Y)\mathscr{C}(X; Y) can converge pointwise to a continuous function without converging uniformly to this function.

For example, on the interval I=[0,1]I = [0, 1], let unu_n be the real-valued function which is equal to 0 for x=0x = 0 and 2/n≤x≤12/n \leq x \leq 1, equal to 1 for x=1/nx = 1/n, and linear in each of the intervals [0,1/n][0, 1/n] and [1/n,2/n][1/n, 2/n]. The sequence (un)(u_n) converges pointwise to 0, but does not converge uniformly to 0 in II (cf. Exercise 6).

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.