G-invariant norms and bicircular projections (CROSBI ID 132358)
Prilog u časopisu | izvorni znanstveni rad | međunarodna recenzija
Podaci o odgovornosti
Fošner, Maja ; Ilišević, Dijana ; Li, Chi-Kwong
engleski
G-invariant norms and bicircular projections
It is shown that for many finite dimensional vector spaces V over C, a linear projection P : V \to V will have nice structure if P + \lambda (I-P) is an isometry for some complex unit not equal to one. From these results, one can readily determine the structure of bicircular projections, i.e., those linear projections P such that P + \mu (I-P) is an isometry for every complex unit \mu. The key ingredient in the proofs is the knowledge of the isometry group of the given norm. The proof techniques also apply to real vector spaces. In such cases, characterizations are given to linear projections P such that P-(I-P)=2P-I is an isometry.
bicircular projection ; symmetric norms ; unitarily invariant norms ; unitary congruence invariant norms ; unitary similarity invariant norms
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Podaci o izdanju
420 (2-3)
2007.
596-608
objavljeno
0024-3795
1873-1856
10.1016/j.laa.2006.08.014