arXiv subjects

R. Lemos

Publications and source records attributed to R. Lemos.

2 recordsLinked to original sources

arXiv2025

Krein Space Numerical Range of Block Matrices -- a Unified Approach to the Hyperbolic Case

In this paper, we investigate the Krein space numerical range of $2$-by-$2$ block matrices, with diagonal blocks as scalar multiples of the identity. For these matrices, we specifically investigate the cases when the respective boundary generating curves consist of hyperbolas. This provides a unified approach to derive established and new results concerning the numerical range hyperbolic shape.

math.FA↗

arXiv2024

Matrices with Hyperbolical Krein Space Numerical Range

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, independently of their size. Ne\-cessary and sufficient conditions for low dimensional tridiagonal matrices to have this shape are obtained only involving the matrix entries

math.FA↗