Product of two matrices similar to companion matrices over sufficiently large fields

In this note, we prove that a square matrix of size $n$ over a field containing at least $2n$ elements can be expressed as the product of two matrices similar to companion matrices, that is to say matrices with the same minimal and characteristic polynomial, if and only if the rank of $A$ is greater than $n-2$, using only elementary facts. We will also give some partial results valid over smaller fields.

Authors

Publication Details

Journal
Zenodo (CERN European Organization for Nuclear Research)
Published
2026-06-18
DOI
https://doi.org/10.5281/zenodo.20744913
Primary Topic
Matrix Theory and Algorithms
Type
preprint
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preprint

Product of two matrices similar to companion matrices over sufficiently large fields

Flavien Mabilat
Zenodo (CERN European Organization for Nuclear Research)
Matrix Theory and Algorithms
preprint

Product of two matrices similar to companion matrices over sufficiently large fields

Flavien Mabilat
preprint en

Abstract

In this note, we prove that a square matrix of size $n$ over a field containing at least $2n$ elements can be expressed as the product of two matrices similar to companion matrices, that is to say matrices with the same minimal and characteristic polynomial, if and only if the rank of $A$ is greater than $n-2$, using only elementary facts. We will also give some partial results valid over smaller fields.

Zenodo (CERN European Organization for Nuclear Research)
Matrix Theory and Algorithms
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