The Jordan canonical form of the Fréchet derivative of a matrix function and the bivariate Jordan problem

Fuente: arXiv
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Auteur principal: Noferini, Vanni
Format: Preprint
Publié: 2025
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author Noferini, Vanni
author_facet Noferini, Vanni
contents Let $\mathbb{F}$ be an algebraically closed field of characteristic $0$. Given a square matrix $A \in \mathbb{F}^{n \times n}$ and a polynomial $f \in \mathbb{F}[w]$, we determine the Jordan canonical form of the formal Fréchet derivative of $f(A)$, in terms of that of $A$ and of $f$. When $\mathbb{F}\subseteq \mathbb{C}$, via Hermite interpolation, our result provides a solution to [N.J. Higham, \emph{Functions of Matrices: Theory and Computation}, Research Problem 3.11]. A generalization consists of finding the Jordan canonical form of linear combinations of Kronecker products of powers of two square matrices, i.e., $\sum_{i,j} a_{ij} (X^i \otimes Y^j)$. For this generalization, we provide some new partial results, including a partial solution under certain assumptions and general bounds on the number and the sizes of Jordan blocks.
format Preprint
id arxiv_https___arxiv_org_abs_2512_08399
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Jordan canonical form of the Fréchet derivative of a matrix function and the bivariate Jordan problem
Noferini, Vanni
Rings and Algebras
Let $\mathbb{F}$ be an algebraically closed field of characteristic $0$. Given a square matrix $A \in \mathbb{F}^{n \times n}$ and a polynomial $f \in \mathbb{F}[w]$, we determine the Jordan canonical form of the formal Fréchet derivative of $f(A)$, in terms of that of $A$ and of $f$. When $\mathbb{F}\subseteq \mathbb{C}$, via Hermite interpolation, our result provides a solution to [N.J. Higham, \emph{Functions of Matrices: Theory and Computation}, Research Problem 3.11]. A generalization consists of finding the Jordan canonical form of linear combinations of Kronecker products of powers of two square matrices, i.e., $\sum_{i,j} a_{ij} (X^i \otimes Y^j)$. For this generalization, we provide some new partial results, including a partial solution under certain assumptions and general bounds on the number and the sizes of Jordan blocks.
title The Jordan canonical form of the Fréchet derivative of a matrix function and the bivariate Jordan problem
topic Rings and Algebras
url https://arxiv.org/abs/2512.08399