Linear operators preserving the higher numerical radius of matrices
- 1 May 1987
- journal article
- research article
- Published by Taylor & Francis in Linear and Multilinear Algebra
- Vol. 21 (1) , 63-73
- https://doi.org/10.1080/03081088708817779
Abstract
A linear operator T on a matrix space is said to be unital if T(I) = I. In this note we characterize the unital lineart operators on matrix spaces that preserve the k-numerical radius. Using the results obtained we easily determine the structure of all linear operators on the space of n × n complex matrices that preserve the k-numerical range. This completes the work of Pierce and Watking, who obtained the results for the cases when n ≠ n2k.Keywords
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