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arXiv math/0509505math.GR
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元素阶已知的有限群的个数

The Number of Finite Groups Whose Element Orders is Given

A. R. Moghaddamfar, W. J. Shi

摘要:

有限群$G$的谱$ω(G)$是$G$的元素阶的集合。如果$Ω$是自然数集合的非空子集,则$h(Ω)$表示有限群$G$与$ω(G)=Ω$的同构类的个数,并放入$h(G)=h(ω(G))$。如果$h(G)=1$,我们说$G$是可识别的(通过光谱$ω(G)$)。$G$组几乎可以识别(分别为)。不可识别),如果$1<h(G)<\infty$(或$h(G)=\infty$)。本文主要研究了射影一般线性群${PGL}(2,p^n)$(其中$p=2^α3^β+1$是素数)、$α\geq 0, β\geq 0$和$n\geq 1$,并证明了这些群几乎不可识别,即$h({PGL}(2,p^n))\in \{1, \infty\}$ .还证明了射影一般线性群${PGL}(2,7)$和${PGL}(2,9)$是不可识别的.本文还提出了一个计算机程序来寻找$a^n-1$的本原素因子。

英文摘要:

The spectrum $ω(G)$ of a finite group $G$ is the set of element orders of $G$. If $Ω$ is a non-empty subset of the set of natural numbers, $h(Ω)$ stands for the number of isomorphism classes of finite groups $G$ with $ω(G)=Ω$ and put $h(G)=h(ω(G))$. We say that $G$ is recognizable (by spectrum $ω(G)$) if $h(G)=1$. The group $G$ is almost recognizable (resp. nonrecognizable) if $1<h(G)<\infty$ (resp. $h(G)=\infty$). In the present paper, we focus our attention on the projective general linear groups ${PGL}(2,p^n)$, where $p=2^α3^β+1$ is a prime, $α\geq 0, β\geq 0$ and $n\geq 1$, and we show that these groups cannot be almost recognizable, in other words $h({PGL}(2,p^n))\in \{1, \infty\}$. It is also shown that the projective general linear groups ${PGL}(2,7)$ and ${PGL}(2,9)$ are nonrecognizable. In this paper a computer program has also been presented in order to find out the primitive prime divisors of $a^n-1$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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