# Proceedings of the American Mathematical Society

Published by the American Mathematical Society since 1950, Proceedings of the American Mathematical Society is devoted to shorter research articles in all areas of pure and applied mathematics.

ISSN 1088-6826 (online) ISSN 0002-9939 (print)

The 2020 MCQ for Proceedings of the American Mathematical Society is 0.85.

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## Cauchy-Schwarz and means inequalities for elementary operators into norm idealsHTML articles powered by AMS MathViewer

by Danko R. Jocić
Proc. Amer. Math. Soc. 126 (1998), 2705-2711 Request permission

## Abstract:

The Cauchy-Schwarz norm inequality for normal elementary operators $\left \Vvert \sum _{n=1}^\infty A_nXB_n \right \Vvert \leq \left \Vvert (\sum _{n=1}^\infty A_n^*A_n)^{1/2}X (\sum _{n=1}^\infty B_n^*B_n)^{1/2} \right \Vvert ,$ implies a means inequality for generalized normal derivations $\left \Vvert \frac {AX+XB}2 \right \Vvert \leq \Vvert X \Vvert ^{1-\frac 1r} \left \Vvert \frac {|A|^rX+X|B|^r}2 \right \Vvert ^\frac 1r,$ for all $r\ge 2$, as well as an inequality for normal contractions $A$ and $B$ $\left \Vvert (I-A^*A) ^\frac 12X(I-B^*B)^\frac 12\right \Vvert \leq \Vvert X-AXB\Vvert ,$ for all $X$ in $B(H)$ and for all unitarily invariant norms $\Vvert \cdot \Vvert .$
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Additional Information
• Danko R. Jocić
• Affiliation: University of Belgrade, Faculty of Mathematics, Studentski trg 16, P. O. Box 550, 11000 Belgrade, Yugoslavia
• Email: jocic@matf.bg.ac.yu
• Received by editor(s): March 12, 1996
• Received by editor(s) in revised form: February 4, 1997
• Communicated by: Palle E. T. Jorgensen
• © Copyright 1998 American Mathematical Society
• Journal: Proc. Amer. Math. Soc. 126 (1998), 2705-2711
• MSC (1991): Primary 47A30; Secondary 47B05, 47B10, 47B15
• DOI: https://doi.org/10.1090/S0002-9939-98-04342-1
• MathSciNet review: 1451812