Bourbaki

Proposition 9

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

Integration, VIII, p. 39, § 4. Convolution of measures and functions

Let f,gf, g be in L(G)\mathscr{L}(G). Assume that the function s↦g(s−1x)f(s)χ(s−1)s \mapsto g(s^{-1}x)f(s)\chi(s^{-1}) is essentially β\beta-integrable except for a locally β\beta-negligible set of values of xx, and that the function

x↦∫∣g(s−1x)f(s)∣χ(s−1) dβ(s), x \mapsto \int |g(s^{-1}x)f(s)|\chi(s^{-1})\, d\beta(s),

defined locally β\beta-almost everywhere, is locally β\beta-integrable. Then ff and gg are convolvable.

This follows from Prop. 1 of No. 1.

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.