PreprintCC BY-NC-ND 4.0arXiv
Zero-trace index of matrices
Abstract
The zero-trace index t(A) of a square complex matrix A is introduced. It is defined as the largest integer k such that A admits a k × k compression with trace zero. This concept is analogous to the zero-dilation index d(A) and is closely related to the k-numerical range. The k-numerical range is characterized as an intersection of half-planes, which is used to derive a formula for t(A) that reduces its computation to the Hermitian case. Conditions for t(A) = d(A) are also established, and matrices satisfying t(A) = n − 1 are characterized. Finally, the zero-trace index is determined for several classes of matrices.
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BibTeX
@misc{rosa2026zerotrace,
title = {{Zero-trace index of matrices}},
author = {Kennett L. Dela Rosa and Eloise P. Misa},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.24486},
eprint = {2610.24486},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.24486},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Zero-trace index of matrices
AU - Kennett L. Dela Rosa
AU - Eloise P. Misa
PY - 2026
DA - 2026/10/17
PB - arXiv
DO - 10.48550/arxiv.2610.24486
UR - https://arxiv.org/abs/2610.24486
AB - The zero-trace index t(A) of a square complex matrix A is introduced. It is defined as the largest integer k such that A admits a k × k compression with trace zero. This concept is analogous to the zero-dilation index d(A) and is closely related to the k-numerical range. The k-numerical range is characterized as an intersection of half-planes, which is used to derive a formula for t(A) that reduces its computation to the Hermitian case. Conditions for t(A) = d(A) are also established, and matrices satisfying t(A) = n − 1 are characterized. Finally, the zero-trace index is determined for several classes of matrices.
ER -