A characterization of maximum norms of commutators of positive contractions

[摘要] 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 1+i/4 parallel to A parallel to parallel to B parallel to or its complex conjugate is in the closure of the numerical range of AB. (C) 2008 Elsevier Inc. All rights reserved.

[发布日期] 2008-12-15

[关键词] norm;commutator;positive operator