Bourbaki

Definition 1

Tag 0892, permanent. Cite it as [Bourbaki, Tag 0892].

Functions of a Real Variable, chapter II, § 3. DERIVATIVES AND INTEGRALS OF FUNCTIONS DEPENDING ON A PARAMETER

One says that the integral ∫Ifα(t) dt\int_I \mathbf{f}_\alpha(t)\,dt is uniformly convergent for α∈A\alpha \in A (or uniformly convergent over AA) if, for every ε>0\varepsilon > 0 there exists a compact interval J0⊂JJ_0 \subset J such that, for every compact interval K⊂IK \subset I with no interior point in common with J0J_0, and every α∈A\alpha \in A, one has

∣∫Kfα(t) dt∣≤ε. \left| \int_K \mathbf{f}_\alpha(t)\,dt \right| \leq \varepsilon.

This definition is equivalent to saying that the family of maps α↦∫Ifα(t) dt\alpha \mapsto \int_I \mathbf{f}_\alpha(t)\,dt is uniformly convergent on AA (towards the map α↦∫Ifα(t) dt\alpha \mapsto \int_I \mathbf{f}_\alpha(t)\,dt) with respect to the filter of sections Φ\Phi of K(I)\mathscr{K}(I); each of the integrals ∫Ifα(t) dt\int_I \mathbf{f}_\alpha(t)\,dt is a fortiori convergent (the converse being false). Further, from what we have just seen (or from Gen. Top., X, p. 281, cor. 2):

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.