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A note on liftings of hermitian elements and unitaries

Published online by Cambridge University Press:  18 May 2009

C. K. Fong
Affiliation:
Department of Mathematics and Statistics, Univeristy of Guelph, Guelph, Ontario, Canada.
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Let A be a complex Banach algebra with unit 1 satisfying ‖1‖ = 1. An element u in A is said to be unitary if it is invertible and ‖u‖ = ‖u−1‖ = 1. An element h in A is said to be hermitian if ‖exp(ifh)‖ = 1 for all real t; that is, exp(ith) is unitary for all real t. Suppose that J is a closed two-sided ideal and π: A → A/J is the quotient mapping. It is easy to see that if x in A is hermitian (resp. unitary), then so is π (x) in A/J. We consider the following general question which is the converse of the above statement: given a hermitian (resp. unitary) element y in A/J, can we find a hermitian (resp. unitary) element x in A such that π(x) = y? (The author has learned that this question, in a more restrictive form, was raised by F. F. Bonsall and that some special cases were investigated; see [1], [2].) In the present note, we give a partial answer to this question under the assumption that A is finite dimensional.

Type
Research Article
Copyright
Copyright © Glasgow Mathematical Journal Trust 1980

References

REFERENCES

1.Allen, G. D. and Ward, J. D., Hermitian liftings in B(lp). To appear.Google Scholar
2.Allen, G. D., Ward, J. D. and Legg, D. A., Hermitian liftings in Orlicz sequence spaces. To appear.Google Scholar
3.Bonsall, F. F. and Duncan, J., Complete normed algebras. Ergebnisse der Mathematik and ihrer Grenzgebiete, Band 80. (Springer-Verlag, 1973).CrossRefGoogle Scholar
4.Sinclair, A. M., Eigenvalues in the boundary of the numerical range, Pacific J. Math. 35 (1970), 231234.CrossRefGoogle Scholar