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Proceedings of the American Mathematical Society
Proceedings of the American Mathematical Society
ISSN 1088-6826(online) ISSN 0002-9939(print)

 

The numerical index of nonselfadjoint operator algebras


Authors: Yoshihiro Nakamura, Kichi-Suke Saito and Kazunari Sakaba
Journal: Proc. Amer. Math. Soc. 117 (1993), 1105-1107
MSC: Primary 47D25; Secondary 46L99, 47A12
MathSciNet review: 1118086
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Abstract: Let $ \mathfrak{A}$ be a (not necessarily selfadjoint) closed subalgebra of $ B(H)$ that is the algebra of all bounded linear operators on a Hilbert space $ H$. In this note, we prove that the range of numerical index of $ \mathfrak{A}$ as an algebra is the whole of the interval $ [\tfrac{1} {2},1]$.


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Additional Information

DOI: http://dx.doi.org/10.1090/S0002-9939-1993-1118086-4
PII: S 0002-9939(1993)1118086-4
Keywords: Operator algebra, numerical index
Article copyright: © Copyright 1993 American Mathematical Society