Disjoint direct product decomposition of permutation groups

Finding direct product decompositions in polynomial time

A polynomial-time algorithm is produced which, given generators for a group of permutations on a finite set, returns a direct product decomposition of the group into directly indecomposable subgroups. The process uses bilinear maps and commutative rings to characterize direct products of p-groups of class 2 and reduces general groups to p-groups using group varieties. The methods apply to quotients of permutation groups and operator groups as well.

Subgroup Chains and Lagrange Coordinatizations of Finite Permutation Groups

We give a general constructive proof for hierarchical coordinatizations (Lagrange Decompositions) of permutation groups. The generalization originates from the investigation of how the subgroup chains of finite permutation groups yield different coordinate systems. The study is motivated by the practical needs and the verification of an existing computational implementation. Large scale machine calculated examples are also presented.

不可约Coxeter群

Irreducible Coxeter groups

证明了非球面不可约Coxeter群是（直接）不可分解的，非球面非仿射Coxeter群是强不可分解的，因为它的有限指数子群是（直接）不可分解的.我们证明了Coxeter群有一个分解为不可分解群的直积，并且这种分解是唯一的，直到一个中心自同构和一个置换的因素。本文证明了Coxeter群有一个虚分解作为强不可分解群的直积，并且这种分解是唯一的，直到可分解和置换的因素。

固有可迁置换群在积作用下包含于圈积的三种类型

Three types of inclusions of innately transitive permutation groups into wreath products in product action

一个置换群是先天传递的，如果它有一个传递的极小正规子群，这个子群称为一个基座。本文研究了在乘积作用下内在传递置换群在圈积中的三种特殊包含。这是通过研究与圈积的积作用相对应的基础集合的自然笛卡尔分解来实现的。以前，我们确定了六类笛卡尔分解，可以采取行动后传递的一个先天的传递群与非阿贝尔基座。本文研究的包裹体对应于六类中的三类。我们发现，在每种情况下的作用群的同构类型是有限的，一些有趣的组合结构是左不变。我们还展示了如何为每种类型构建包含体的示例。

Non-Nudgable Subgroups of Permutations

Motivated by a problem from behavioral economics, we study subgroups of permutation groups that have a certain strong symmetry. Given a fixed permutation, consider the set of all permutations with disjoint inversion sets. The group is called non-nudgable, if the cardinality of this set always remains the same when replacing the initial permutation with its inverse. It is called nudgable otherwise. We show that all full permutation groups, standard dihedral groups, half of the alternating groups, and any abelian subgroup are non-nudgable. In the right probabilistic sense, it is thus quite likel…

A decomposition theorem for higher rank Coxeter groups

In this paper, we show that any Coxeter graph which defines a higher rank Coxeter group must have disjoint induced subgraphs each of which defines a hyperbolic or higher rank Coxeter group. We then use this result to demonstrate several classes of Coxeter graphs which define hyperbolic Coxeter groups.

Asymmetric coloring of locally finite graphs and profinite permutation groups: Tucker's Conjecture confirmed

An asymmetric coloring of a graph is a coloring of its vertices that is not preserved by any non-identity automorphism of the graph. The motion of a graph is the minimal degree of its automorphism group, i.e., the minimum number of elements displaced by any non-identity automorphism. In this paper we confirm Tom Tucker's "Infinite Motion Conjecture" that connected locally finite graphs with infinite motion admit an asymmetric 2-coloring. We infer this from the more general result that the inverse limit of a sequence of finite permutation groups with disjoint domains, viewed as a permutation gr…

Primitive permutation groups of degree 3p

This paper presents an analysis of primitive permutation groups of degree $3p$, where $p$ is a prime number, analogous to H. Wielandt's treatment of groups of degree $2p$. It is also intended as an example of the systematic use of combinatorial methods as surveyed in \S6 for distilling information about a permutation group from knowledge of the decomposition of its character. The work is organised into three parts. Part I contains the lesser half of the calculation, the determination of the decomposition of the permutation character. Part II contains a survey of the combinatorial methods and, …

泛幻方排列与N元群

Panmagic permutations and N-ary groups

研究泛幻方排列的代数结构，发现其仿射子集在多元乘法下具有特殊性质，并与数论中的乘法阶、4k+1素数等经典主题相关联。

基于Post陪集定理的泛幻排列的N元群

N-ary groups of panmagic permutations from the Post coset theorem

研究泛幻排列（模n皇后问题的解）的代数结构，通过Post陪集定理证明其构成二面体子群陪集的N元群推广，并揭示与数论和组合学的联系。

Virtual permutations and polymorhisms

There is a natural map from a symmetric group $S_n$ to a smaller symmetric group $S_{n-1}$, we write a decomposition of a permutation into a product of disjoint cycles and remove the element $n$ from this expression. For this reason there exists the inverse limit $\mathfrak{S}$ of sets $S_n$. We equip $S_n$ with the uniform distribution (or more generally with an Ewens distribution) and get a structure of a measure space on $\mathfrak{S}$ (it is called 'virtual permutations' or 'Chinese restaurant process'), a double $S_\infty\times S_\infty $ of an infinite symmetric group acts on $\mathfrak{…