Bourbaki

Proposition 12

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

Integration, VIII, p. 23, § 3. Convolution of measures on groups

If λ∈C′(G)\lambda \in \mathscr{C}'(G) and μ∈M(X)\mu \in \mathscr{M}(X), then

γ(λ)μ=λ∗μ. \gamma(\lambda)\mu = \lambda * \mu.

By Prop. 7 of §1, No. 5,

λ∗μ=∫G(εs∗μ)dλ(s). \lambda * \mu = \int_G (\varepsilon_s * \mu) d\lambda(s).

Now, εs∗μ=γ(s)μ\varepsilon_s * \mu = \gamma(s)\mu (No. 2, formula (5)) and

∫G(γ(s)μ)dλ(s)=γ(λ)μ \int_G (\gamma(s)\mu) d\lambda(s) = \gamma(\lambda)\mu

by the definition of γ(λ)\gamma(\lambda).

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.