Spectrum of a C*-algebra

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The set of unitary equivalence classes of irreducible representations of the -algebra. The spectrum can be topologized if one declares that the closure of a subset is the family of all (equivalence classes of) representations whose kernels contain the intersection of the kernels of all the representations of this subset. For a commutative -algebra, the resulting topological space coincides with the space of characters (which is homeomorphic to the space of maximal ideals, cf. Character of a -algebra; Maximal ideal). In the general case, the spectrum of a -algebra is the basis for decomposing its representations into direct integrals of irreducible representations.


[1] J. Dixmier, " algebras" , North-Holland (1977) (Translated from French)


This topology on the spectrum of a -algebra is called the hull-kernel topology, or Jacobson topology.


[a1] W. Arveson, "An invitation to -algebras" , Springer (1976) pp. Chapts. 3–4
[a2] G.K. Pedersen, "-algebras and their automorphism groups" , Acad. Press (1979) pp. §4.1
How to Cite This Entry:
Spectrum of a C*-algebra. Encyclopedia of Mathematics. URL:*-algebra&oldid=15237
This article was adapted from an original article by V.S. Shul'man (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article