Bourbaki

Corollary

Tag 02V0, permanent. Cite it as [Bourbaki, Tag 02V0].

Théories spectrales, chapter III, § 6. Propriétés spectrales des endomorphismes des espaces de Banach

Let u∈L(E)u\in \mathscr{L}(E). If uu is normal, then Sp0(u)_0(u) is empty, and if uu is hermitian, then Spe(u)_e(u) coincides with the spectrum of π(u)\pi (u) relative to the algebra C\mathscr{C}alk(E).

Both assertions result from the proposition and from the definition of the sets Spn(u)_n(u) for n∈Z‾n\in \overline{\mathbf{Z}} and of Spω(u)_{\omega}(u), which form a partition of the essential spectrum of uu (def. 2 of III, p. 83).

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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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.