The Degrees Of Toroidal Regular Proper Hypermaps

环面地图与超地图的保向自同构群的度数

The degrees of the orientation-preserving automorphism groups of toroidal maps and hypermaps

本文研究高度对称的环面地图与超地图的保向自同构群的忠实传递置换表示，给出所有可能的度数列表，并利用GAP包corefreesub构造Schreier陪集图。

Duality on hypermaps with symmetric or alternating monodromy group

Duality is the operation that interchanges hypervertices and hyperfaces on oriented hypermaps. The duality index measures how far a hypermap is from being self-dual. We say that an oriented regular hypermap has \emph{duality-type} $\{l,n\}$ if $l$ is the valency of its vertices and $n$ is the valency of its faces. Here, we study some properties of this duality index in oriented regular hypermaps and we prove that for each pair $n$, $l \in \mathbb{N}$, with $n,l \geq 2$, it is possible to find an oriented regular hypermap with extreme duality index and of duality-type $\{l,n \}$, even if we are…

Symmetries of quasiplatonic Riemann surfaces

We state and prove a corrected version of a theorem of Singerman, which relates the existence of symmetries (anticonformal involutions) of a quasiplatonic Riemann surface $\mathcal S$ (one uniformised by a normal subgroup $N$ of finite index in a cocompact triangle group $Δ$) to the properties of the group $G=Δ/N$. We give examples to illustrate the revised necessary and sufficient conditions for the existence of symmetries, and we relate them to properties of the associated dessins d'enfants, or hypermaps.

Classification of finite groups with toroidal or projective-planar permutability graphs

Let $G$ be a group. The permutability graph of subgroups of $G$, denoted by $Γ(G)$, is a graph having all the proper subgroups of $G$ as its vertices, and two subgroups are adjacent in $Γ(G)$ if and only if they permute. In this paper, we classify the finite groups whose permutability graphs are toroidal or projective-planar. In addition, we classify the finite groups whose permutability graph does not contain one of $K_{3,3}$, $K_{1,5}$, $C_6$, $P_5$, or $P_6$ as a subgraph.

Non-solvable graphs of groups

Let $G$ be a group and $Sol(G)=\{x \in G : \langle x,y \rangle \text{ is solvable for all } y \in G\}$. We associate a graph $\mathcal{NS}_G$ (called the non-solvable graph of $G$) with $G$ whose vertex set is $G \setminus Sol(G)$ and two distinct vertices are adjacent if they generate a non-solvable subgroup. In this paper we study many properties of $\mathcal{NS}_G$. In particular, we obtain results on vertex degree, cardinality of vertex degree set, graph realization, domination number, vertex connectivity, independence number and clique number of $\mathcal{NS}_G$. We also consider two grou…