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arXiv 2005.07846math.COmath.NT
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有限域上矩阵的Jordan-Landau定理

Jordan--Landau theorem for matrices over finite fields

Gilyoung Cheong, Jungin Lee, Hayan Nam, Myungjun Yu

摘要:

给定一个正整数$r$和一个素数幂$q$,当$n$较大时,我们估计了随机矩阵$A$在$\mathrm{GL}_{n}(\mathbb{F}_{q})$中的特征多项式$f_{A}(t)$是无平方因子且有$r$(monic)不可约因子的概率.我们还估计了类似的概率,$f_{A}(t)$有$r$不可约因子计数的多重性。在任何一种情况下,主项$(\log n)^{r-1}((r-1)!n)^{-1}$和误差项$O((\log n)^{r-2}n^{-1})$(其隐含常数仅取决于$r$,而不取决于$q$或$n$)与$n$字母上的随机置换是$r$不相交循环的乘积的概率一致。我们证明的主要成分是一个递归参数由于S。D. Cohen,它以前用于估计$\mathbb{F}_{q}[t]$中的随机度$n$一元多项式是无平方的且具有$r$不可约因子的概率,以及多项式具有$r$不可约因子且具有多重性的类似概率。我们得到我们的结果通过仔细修改科恩的递归参数在矩阵设置,使用赖纳定理,计数的数目$n \times n$矩阵与一个固定的特征多项式超过$\mathbb{F}_{q}$。

英文摘要:

Given a positive integer $r$ and a prime power $q$, we estimate the probability that the characteristic polynomial $f_{A}(t)$ of a random matrix $A$ in $\mathrm{GL}_{n}(\mathbb{F}_{q})$ is square-free with $r$ (monic) irreducible factors when $n$ is large. We also estimate the analogous probability that $f_{A}(t)$ has $r$ irreducible factors counting with multiplicity. In either case, the main term $(\log n)^{r-1}((r-1)!n)^{-1}$ and the error term $O((\log n)^{r-2}n^{-1})$, whose implied constant only depends on $r$ but not on $q$ nor $n$, coincide with the probability that a random permutation on $n$ letters is a product of $r$ disjoint cycles. The main ingredient of our proof is a recursion argument due to S. D. Cohen, which was previously used to estimate the probability that a random degree $n$ monic polynomial in $\mathbb{F}_{q}[t]$ is square-free with $r$ irreducible factors and the analogous probability that the polynomial has $r$ irreducible factors counting with multiplicity. We obtain our result by carefully modifying Cohen's recursion argument in the matrix setting, using Reiner's theorem that counts the number of $n \times n$ matrices with a fixed characteristic polynomial over $\mathbb{F}_{q}$.

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