Numerical radius inequality for C-0 contractions

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/27954

Title:	Numerical radius inequality for C-0 contractions
Authors:	Wu,PY;Gau,HL;Tsai,MC
Contributors:	數學研究所
Keywords:	MAPPING THEOREMS;RANGE;PRODUCT
Date:	2009
Issue Date:	2010-06-29 19:38:48 (UTC+8)
Publisher:	中央大學
Abstract:	We show that if A is a C-0 contraction with minimal function phi such that w(A) = w(S(phi)), where w(.) denotes the numerical radius of an operator and S(phi) is the compression of the shift on (HH2)-H-2 circle minus phi, and B commutes with A, then w(AB) <= w(A)parallel to B parallel to. This is in contrast to the known fact that if A = S(phi) (even on dimensional space) and B commutes with A, then w(AB) <= w parallel to A parallel to w(B) is not necessarily true. As a a finite consequence, we have w(AB) <= w(A)parallel to B parallel to for any quadratic operatorA and any B commuting with A. (c) 2007 Elsevier Inc. All rights reserved.
Relation:	LINEAR ALGEBRA AND ITS APPLICATIONS
Appears in Collections:	[Graduate Institute of Mathematics] journal & Dissertation

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