Distribution of matrices over $\mathbb{F}_q[x]$

In this paper, we count the number of matrices $A = (A_{i,j} )\in \mathcal{O} \subset \mathrm{Mat}_{n\times n}(\mathbb{F}_q[x])$ where $\deg (A_{i,j})\le k, 1\le i,j\le n$, $\deg (\det A) = t$, and $\mathcal{O}$ is a given orbit of $\mathrm{GL}_n(\mathbb{F}_q[x])$. By an elementary argument, we show...

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Bibliographic Details
Main Author: Ji, Yibo
Format: Article
Language:English
Published: Académie des sciences 2024-10-01
Series:Comptes Rendus. Mathématique
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Online Access:https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.616/
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Summary:In this paper, we count the number of matrices $A = (A_{i,j} )\in \mathcal{O} \subset \mathrm{Mat}_{n\times n}(\mathbb{F}_q[x])$ where $\deg (A_{i,j})\le k, 1\le i,j\le n$, $\deg (\det A) = t$, and $\mathcal{O}$ is a given orbit of $\mathrm{GL}_n(\mathbb{F}_q[x])$. By an elementary argument, we show that the above number is exactly $\# \mathrm{GL}_n(\mathbb{F}_q)\cdot q^{(n-1)(nk-t)}$. This formula gives an equidistribution result over $\mathbb{F}_q[x]$, which is an analogue, in strong form, of a result over $\mathbb{Z}$ proved in [2] and [3].
ISSN:1778-3569