scholarly journals Additive mappings that preserve rank one nilpotent operators

2003 ◽  
Vol 367 ◽  
pp. 213-224 ◽  
Author(s):  
Wu Jing ◽  
Pengtong Li ◽  
Shijie Lu
1995 ◽  
Vol 47 (4) ◽  
pp. 841-851 ◽  
Author(s):  
Gordon W. Macdonald

AbstractThe distance from an arbitrary rank-one projection to the set of nilpotent operators, in the space of k × k matrices with the usual operator norm, is shown to be sec(π/(k:+2))/2. This gives improved bounds for the distance between the set of all non-zero projections and the set of nilpotents in the space of k × k matrices. Another result of note is that the shortest distance between the set of non-zero projections and the set of nilpotents in the space of k × k matrices is .


1993 ◽  
Vol 182 ◽  
pp. 239-256 ◽  
Author(s):  
Matjaž Omladič ◽  
Peter Šemrl
Keyword(s):  
Rank One ◽  

2002 ◽  
Vol 348 (1-3) ◽  
pp. 175-187 ◽  
Author(s):  
Bojan Kuzma
Keyword(s):  
Rank One ◽  

2020 ◽  
pp. 1-21
Author(s):  
Zachary Cramer

Abstract Building on MacDonald’s formula for the distance from a rank-one projection to the set of nilpotents in $\mathbb {M}_n(\mathbb {C})$ , we prove that the distance from a rank $n-1$ projection to the set of nilpotents in $\mathbb {M}_n(\mathbb {C})$ is $\frac {1}{2}\sec (\frac {\pi }{\frac {n}{n-1}+2} )$ . For each $n\geq 2$ , we construct examples of pairs $(Q,T)$ where Q is a projection of rank $n-1$ and $T\in \mathbb {M}_n(\mathbb {C})$ is a nilpotent of minimal distance to Q. Furthermore, we prove that any two such pairs are unitarily equivalent. We end by discussing possible extensions of these results in the case of projections of intermediate ranks.


Author(s):  
Najat Muthana ◽  
◽  
Asma Ali ◽  
Kapil Kumar

1970 ◽  
Vol 11 (8) ◽  
pp. 2415-2424 ◽  
Author(s):  
M. Anthea Grubb ◽  
D. B. Pearson

1972 ◽  
Vol 46 ◽  
pp. 97-109
Author(s):  
Susan Williamson

Let k denote the quotient field of a complete discrete rank one valuation ring R of unequal characteristic and let p denote the characteristic of R̅; assume that R contains a primitive pth root of unity, so that the absolute ramification index e of R is a multiple of p — 1, and each Gallois extension K ⊃ k of degree p may be obtained by the adjunction of a pth root.


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