Better bounds on the numerical radii of Hilbert space operators

被引：28
|
作者：
Omidvar, Mohsen Erfanian [1 ]
Moradi, Hamid Reza [2 ]
机构：
[1] Islamic Azad Univ, Mashhad Branch, Dept Math, Mashhad, Razavi Khorasan, Iran
[2] Islamic Azad Univ, Mashhad Branch, Young Researchers & Elite Club, Mashhad, Razavi Khorasan, Iran
来源：
LINEAR ALGEBRA AND ITS APPLICATIONS | 2020年 / 604卷
关键词：
Numerical radius; Operator norm; Operator convex function; Hermite-Hadamard inequality; NORM INEQUALITIES;
D O I：
10.1016/j.laa.2020.06.021
中图分类号：
O29 [应用数学];
学科分类号：
070104 ;
摘要：
Kittaneh proved that if A is a bounded linear operator on a complex Hilbert space, then 1/4 parallel to vertical bar A vertical bar(2) + vertical bar A*vertical bar(2)parallel to <= omega(2) (A), where omega(.) and parallel to.parallel to are the numerical radius and the usual operator norm, and vertical bar A vertical bar = (A*A)(1/2). In this paper, we show that 1/4 parallel to vertical bar A vertical bar(2) + vertical bar A vertical bar(2)parallel to <= 1/2 omega(2) (A)+1/8 parallel to(A+A*) (A-A*)parallel to <=omega(2) (A) Meanwhile, we give an improvement of the norm inequality presented by Bhatia and Kittaneh for the positive operators. (C) 2020 Elsevier Inc. All rights reserved.
引用
收藏
页码：265 / 277
页数：13
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