A characterization of maximum norms of commutators of positive contractions |
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| Authors: | Yue-Qing Wang Hong-Ke Du |
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| Affiliation: | a Department of Mathematics and Physics, Chongqing University of Science and Technology, Chong'qing 400042, PR China
b College of Mathematics and Information Science, Shaanxi Normal University, Xi'an 710062, PR China |
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| Abstract: | In this note, we give a characterization of a pair (A,B) of positive contractions with commutator AB−BA of maximum possible norm. A necessary and sufficient condition is that either  or its complex conjugate is in the closure of the numerical range of AB. |
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| Keywords: | Norm Commutator Positive operator |
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