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arXiv 2602.22876math.GRmath.CO
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无限群中的因素

Factors in infinite groups

Mikhail Kabenyuk

AI总结:

该研究证明了每个无限群都是不稳定的,通过图论方法展示了存在某些子集使得最大直积子集的基数不一致,反驳了Kourovka笔记中的问题21.58。

摘要:

设G为一个群,A为G的一个非空子集。与A相关的右s-因子是G的一个最大子集U,使得乘积AU是直积。下s-指数|G:A|^-和上s-指数|G:A|+定义为这样的最大集合U的基数的最小值和上确界。如果|G:A|^-等于|G:A|+,则称A为稳定的子集,若G中的每一个子集都是稳定的,则称G为稳定的。通过将问题重新表述为Cayley图的图论方法,我们证明了每一个无限群都是不稳定的。等价地,对于每一个无限群G,存在一个子集A⊆G,使得具有直积AU的最大子集U的基数不全相同。这给出了Kourovka笔记中问题21.58的否定回答。

英文摘要:

Let $G$ be a group and $A\subseteq G$ a non-empty subset. A right $s$-factor associated with $A$ is a maximal subset $U\subseteq G$ such that the product $AU$ is direct. The lower and upper $s$-indices $|G:A|^-$ and $|G:A|^+$ are defined as the minimum and the supremum of the cardinalities of such maximal sets $U$. The subset $A$ is called stable if $|G:A|^- = |G:A|^+$, and $G$ is called stable if every subset of $G$ is stable. Using a graph-theoretic reformulation in terms of Cayley graphs, we prove that every infinite group is unstable. Equivalently, for every infinite group $G$ there exists a subset $A\subseteq G$ for which maximal subsets $U$ with direct product $AU$ do not all have the same cardinality. This gives a negative answer to Question 21.58 of the Kourovka Notebook.

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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