Abstract
Let R be a proper subset of the complex plane, and let SRbe the set of n × n complex matrices A such that the numerical range W(A) satisfies W(A) ⊆ R. Linear maps φ on matrices satisfying φ(SR) = SRare characterized. Denote by S̃Rthe set of n × n complex matrices A such that the numerical radius r(A) satisfies r(A) ⊆ R for a proper subset R of nonnegative real numbers. Linear maps φ on matrices satisfying φ(S̃R) = S̃Rare also characterized. Analogous results on Hermitian matrices are obtained.
| Original language | English |
|---|---|
| Pages (from-to) | 235-249 |
| Number of pages | 15 |
| Journal | Linear and Multilinear Algebra |
| Volume | 52 |
| Issue number | 3-4 |
| DOIs | |
| Publication status | Published - 1 Jan 2004 |
| Externally published | Yes |
Keywords
- Hermitian matrices
- Linear maps
- Numerical range (radius)
ASJC Scopus subject areas
- Algebra and Number Theory