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arXiv · 1707.05469

A Resolvent Criterion for Normality

Cara D. Brooks·Alberto A. Condori
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Abstract

Given a normal matrix $A$ and an arbitrary square matrix $B$ (not necessarily of the same size), what relationships between $A$ and $B$, if any, guarantee that $B$ is also a normal matrix? We provide an answer to this question in terms of pseudospectra and norm behavior. In doing so, we prove that a certain distance formula, known to be a necessary condition for normality, is in fact sufficient and demonstrates that the spectrum of a matrix can be used to recover the spectral norm of its resolvent precisely when the matrix is normal. These results lead to new normality criteria and other interesting consequences.

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BibTeXRIS

Cara D. Brooks, Alberto A. Condori. 2017-07-18. A Resolvent Criterion for Normality. https://arxiv.org/abs/1707.05469

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