Acta Mathematica Sinica

, Volume 11, Issue 4, pp 389–398 | Cite as

Normality preserving multiplication operators

  • Lu Shijie 
  • Lu Fangyan 


We show that a multiplication operator Φ(T)=ATB is normality preserving if and only if it is hyponormality preserving, if and only if it is either of the formA=fg,B=hf, orA=D,B=λD* for someλ∈C andD* D=I. Also we show that Φ is (semi-) Fredholmness prserving if and only ifA andB are (semi-) Fredholm operators.


Multiplication operators Normality preserving Fredholmness preserving 


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Copyright information

© Science Press 1995

Authors and Affiliations

  • Lu Shijie 
    • 1
  • Lu Fangyan 
    • 1
  1. 1.Department of MathematicsZhejiang UniversityHangzhouChina

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