Circular numerical ranges of partial isometries

Please use this identifier to cite or link to this item: https://ir.lib.ncu.edu.tw/handle/987654321/109175

Title:	Circular numerical ranges of partial isometries
Authors:	高華隆;Gau, Hwa-Long;Wang, Kuo-Zhong;Wu, Pei Yuan
Contributors:	理學院數學系
Keywords:	Algebra;Circularity;Discs;Intervals;Invariance;irreducible matrix;nilpotent matrix;numerical range;Origins;partial isometry;Rotational;rotationally invariant matrix
Date:	2016-01-02
Issue Date:	2026-04-23 16:12:11 (UTC+8)
Publisher:	Taylor and Francis Ltd.;Abingdon: Taylor & Francis
Abstract:	摘要： Let be an -by- partial isometry whose numerical range is a circular disc with centre and radius . In this paper, we are concerned with the possible values of and . We show that must be if is at most and conjecture that the same is true for the general . As for the radius, we show that if , then the set of all possible values of is . Indeed, it is shown more precisely that for , , the possible values of are those in the interval . In the proof process, we also characterize -by- partial isometries which are (unitarily) irreducible. The paper is concluded with a question on the rotational invariance of nilpotent partial isometries with circular numerical ranges centred at the origin. 出版者： Abingdon: Taylor & Francis 出版日期： 2016-01-02 出處： Linear & multilinear algebra, 2016-01, Vol.64 (1), p.14-35 版權： 2015 Taylor & Francis 2015 版權： 2015 Taylor & Francis 識別號： ISSN: 0308-1087 識別號： EISSN: 1563-5139 識別號： DOI: 10.1080/03081087.2014.1003530
Appears in Collections:	[Department of Mathematics] journal & Dissertation

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