Bourbaki

Remark

Tag 03B2, permanent. Cite it as [Bourbaki, Tag 03B2].

Théories spectrales, chapter V, § 2. Représentations des groupes localement compacts

Let χ\chi be a character of G. If G is not compact, the χ\chi-isotypical component of the regular representation of G in L2(G)L^2(G) is trivial. If G is compact, the χ\chi-isotypical component of the regular representation of G is of dimension 1 and the function χ∈L2(G)\chi \in L^2(G) is a basis of it.

Bourbaki sets the proof directly after the statement, and the corpus does not separate them, so what is above is the statement and its proof together.

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Cites

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Machine translation of the English, by gpt-5.4, gpt-5-6-mini, against glossary version 34. Not checked by a person. That model is a cut down version of the one the rest of this language was written by.