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Akhlaq A. Siddiqui
Computation of the λu-function in JB*-algebras view print
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Published: |
May 22, 2013 |
Keywords: |
C*-algebra; JB*-algebra; unit ball; invertible element; unitary element; unitary isotope; convex hull; λu-function |
Subject: |
17C65, 46L05, 46H70 |
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Abstract
Motivated by the work of Gert K. Pedersen on a geometric function, which is defined on the unit ball of a C*-algebra and
called the λu-function, the present author recently initiated a study of the λu-function in the more general setting of JB*-algebras. He used his earlier results on the geometry of the unit ball to investigate certain convex combinations of elements in a JB*-algebra and to obtain analogues of some related C*-algebra results, including a formula to compute λu-function on invertible elements in a JB*-algebra. The main purpose in this article is to investigate the computation of the λu-function on noninvertible elements in the unit ball of a JB*-algebra. Additional results that relate the λu-function to convex combinations, unitary rank, and distance to the invertibles in the C*-algebra setting are generalized to the JB*-algebra context. Results of G. K. Pedersen and M. Rordam are generalized. An open problem is presented.
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Author information
Department of Mathematics, College of Science, King Saud University, P.O. Box 2455-5, Riyadh-11451, Kingdom of Saudi Arabia.
asiddiqui@ksu.edu.sa
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