Normality preserving multiplication operators |
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| Authors: | Shijie Lu Fangyan Lu |
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| Institution: | (1) Department of Mathematics, Zhejiang University, 310027 Hangzhou, China |
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| Abstract: | We show that a multiplication operator  (T)=ATB is normality preserving if and only if it is hyponormality preserving, if and only if it is either of the formA=f g,B=h f, orA=D,B= D* for some C andD* D=I. Also we show that is (semi-) Fredholmness prserving if and only ifA andB are (semi-) Fredholm operators.Supported by the Science Foundation of Zhejiang Province and NSF. |
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| Keywords: | Multiplication operators Normality preserving Fredholmness preserving |
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