Exterior numerical radii and antiinvariant subspaces | |
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學年 | 86 |
學期 | 2 |
出版(發表)日期 | 1998-07-01 |
作品名稱 | Exterior numerical radii and antiinvariant subspaces |
作品名稱(其他語言) | |
著者 | 譚必信; Tam, Bit-shun |
單位 | 淡江大學數學學系 |
出版者 | Taylor & Francis |
著錄名稱、卷期、頁數 | Linear and Multilinear Algebra 44(3), pp.195-245 |
摘要 | Let m be a positive integer less than n, and let A B be n×n complex matrices. The mth A-exterior numerical radius of B is defined as where Cm( A) is the mth compound matrix of A and Un is the group of n×n unitary matrices. Marcus and Sandy conjectured that a (necessary and) sufficient condition for to imply that the rank of B is less than m is that A is nonscalar and counter-example to the conjecture was given in [10]. In this paper, using geometric arguments, we show that the conjecture is true in the special case when A is of rank m. Then we prove that in order that for each B of rank m it is necessary and sufficient that rank A≤m and rank (A—λI)≤min{m, n—m) for all complex numbers λ. We also find other equivalent conditions one of which is that, for any pair of linear subspaces X 9 Y of Cn with dim X= m and dim Y =n— m, there exists UεUn such that Cn = AU(X)⊗U(Y). To establish the equivalence of the above conditions, we give a structure theory of the anti-invariance of matrices, which relies on a combinatorial method and the use of gap between subspaces. As by-products, we obtain two interesting results about matchings of a multi-set. The cases when Unis replaced by GL(n, C) or the underlying field is the set of real numbers are also examined carefully. Some open problems are posed at the end. |
關鍵字 | mth A-exterior numerical radius;Marcus and Sandy conjecture;matching of a multi-set;antiinvariant subspace;gap between subspaces |
語言 | en |
ISSN | 0308-1087 |
期刊性質 | 國內 |
收錄於 | |
產學合作 | |
通訊作者 | |
審稿制度 | 否 |
國別 | TWN |
公開徵稿 | |
出版型式 | ,電子版 |
相關連結 |
機構典藏連結 ( http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/41412 ) |