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A problem on the Riesz-Dunford operator calculus and convex univalent functions

Published online by Cambridge University Press:  18 May 2009

J. S. Hwang
Affiliation:
Institute of Mathematics, Academia Sinica Taipei, Taiwan.
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In his paper [3], Ky Fan asked whether if f is a convex univalent function in the unit disk, with f(0) = 0 and f'(0) = 1, then is it true that the set of f(A) is a convex set of operators, when A runs through all proper contractions on a Hilbert space? We answer this question in the negative.

Type
Research Article
Copyright
Copyright © Glasgow Mathematical Journal Trust 1983

References

REFERENCES

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2.Dunford, N. and Schwartz, J. T., Linear operators, Part I: General theory. (Interscience, 1958).Google Scholar
3.Fan, Ky, Analytic functions of a proper contraction, Math. Z. 160, (1978) 275290.CrossRefGoogle Scholar
4.Hille, E., Analytic function theory II. (Ginn, 1962).Google Scholar