3 papers
math.FA2026
On the ellipticity of the higher rank numerical range
Natália Bebiano, Rute Lemos, Graça Soares
The higher rank numerical range is a concept that generalizes the classical numerical range, and it has application in quantum error correction. We investigate these sets for -b…
math.FA2025
Krein Space Numerical Range of Block Matrices -- a Unified Approach to the Hyperbolic Case
N. Bebiano, R. Lemos, G. Soares
In this paper, we investigate the Krein space numerical range of -by- block matrices, with diagonal blocks as scalar multiples of the identity. For these matrices, we specifi…
math.FA2024
Matrices with Hyperbolical Krein Space Numerical Range
N. Bebiano, R. Lemos, G. Soares
This paper is devoted to matrices with hyperbolical Krein space numerical range. This shape characterizes the 2-by-2 case and persists for certain classes of matrices, independentl…