We show that a compact operator A is a multiple of a positive semi-definite operator if and only if sigma(AB) subset of <(W(A)W(B))over bar>, for all (rank one) operators B. An example of a normal operator is given to show that the equivalence conditions may fail in general. We then obtain conditions to identify other classes of operators A so that equivalence conditions hold. (C) 2014 Elsevier Inc. All rights reserved.
机构:
Shaanxi Normal Univ, Coll Math & Informat Sci, Xian 710062, Peoples R ChinaShaanxi Normal Univ, Coll Math & Informat Sci, Xian 710062, Peoples R China
Du, Hongke
Li, Chi-Kwong
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机构:
Coll William & Mary, Dept Math, Williamsburg, VA 23187 USAShaanxi Normal Univ, Coll Math & Informat Sci, Xian 710062, Peoples R China
Li, Chi-Kwong
Wang, Kuo-Zhong
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机构:
Natl Chiao Tung Univ, Dept Appl Math, Hsinchu 30010, TaiwanShaanxi Normal Univ, Coll Math & Informat Sci, Xian 710062, Peoples R China
Wang, Kuo-Zhong
Wang, Yueqing
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机构:
Chongqing Univ Sci & Technol, Dept Math & Phys, Chongqing 401331, Peoples R ChinaShaanxi Normal Univ, Coll Math & Informat Sci, Xian 710062, Peoples R China
Wang, Yueqing
Zuo, Ning
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Chongqing Univ Sci & Technol, Dept Math & Phys, Chongqing 401331, Peoples R ChinaShaanxi Normal Univ, Coll Math & Informat Sci, Xian 710062, Peoples R China
Zuo, Ning
OPERATORS AND MATRICES,
2017,
11
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: 171
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180
机构:Univ Tras Os Montes & Alto Douro, Dept Math, P-5000911 Vila Real, Portugal
Lemos, R
da Providência, J
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机构:Univ Tras Os Montes & Alto Douro, Dept Math, P-5000911 Vila Real, Portugal
da Providência, J
Soares, G
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Univ Tras Os Montes & Alto Douro, Dept Math, P-5000911 Vila Real, PortugalUniv Tras Os Montes & Alto Douro, Dept Math, P-5000911 Vila Real, Portugal