Bourbaki

Remark

Tag 09K8, permanent. Cite it as [Bourbaki, Tag 09K8].

Integration, VIII, p. 28, § 4. Convolution of measures and functions

The hypothesis (iii) of Prop. 2 is satisfied notably when μ\mu is bounded. For, for every n>0n > 0, there then exists a compact subset KnK_n of GG such that

∣μ∣(G−Kn)≤1n |\mu|(G - K_n) \leq \frac{1}{n}
(Ch. IV, §4, No. 7), and μ\mu is carried by the union of the KnK_n. More generally, let ρ\rho be a lower semi-continuous finite function >0> 0 on GG such that ρ(st)≤ρ(s)ρ(t)\rho(st) \leq \rho(s)\rho(t); if μ∈Mρ\mu \in \mathscr{M}^\rho, the hypothesis (iii) is satisfied; for, ρ⋅μ\rho \cdot \mu is bounded, and μ\mu is carried by the same subsets as ρ⋅μ\rho \cdot \mu since, on every compact subset of GG, ρ\rho is bounded below by a constant >0> 0.

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.