Bourbaki

Corollary 1

Tag 02T5, permanent. Cite it as [Bourbaki, Tag 02T5].

Théories spectrales, chapter III, § 4. Perturbations dans les espaces de Banach

The functions defined by u↦u\mapsto dim Ker(uu) and by u↦u\mapsto dim Coker(uu) on QM(E;F)\mathscr{Q}\mathscr{M}(E; F) are upper semi-continuous. The function u↦u\mapsto ind(uu) is locally constant on QM(E;F)\mathscr{Q}\mathscr{M}(E; F).

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, against glossary version 34. Not checked by a person.