An invariant for certain operator algebras - PubMed (original) (raw)

An invariant for certain operator algebras

R W Carey et al. Proc Natl Acad Sci U S A. 1974 May.

Abstract

It is shown that the so-called principal function invariant, which is associated in a unitarily invariant way to operators with trace class self commutator TT(*) - T(*)T, is invariant under trace class perturbations of T and is an extension of the index of T-z to the whole plane. The connection of the principal function, under additional hypothesis, with the determination of the maximal ideal space of the C(*) algebra generated by T is discussed, and it is shown that the principal function, even when it takes noninteger values, plays a role in establishing the existence of invariant subspaces for T and in determining the point spectrum of T.

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References

    1. Proc Natl Acad Sci U S A. 1971 Aug;68(8):1684-5 - PubMed

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