The relative neighbourhood graph of a finite planar set

The relative neighbourhood graph of a finite planar set

The relative neighbourhood graph (RNG) of a set of n points on the plane is defined. The ability of the RNG to extract a perceptually meaningful structure from the set of points is briefly discussed and compared to that of two other graph structures: the minimal spanning tree (MST) and the Delaunay (Voronoi) triangulation (DT). It is shown that the RNG is a superset of the MST and a subset of t...

Good approximations for the relative neighbourhood graph

On the planarity of a graph related to the join of subgroups of a finite group

‎Let $G$ be a finite group which is not a cyclic $p$-group‎, ‎$p$ a prime number‎. ‎We define an undirected simple graph $Delta(G)$ whose‎ ‎vertices are the proper subgroups of $G$, which are not contained in the‎ ‎Frattini subgroup of $G$ and two vertices $H$ and $K$ are joined by an edge‎ ‎if and only if $G=langle H‎ , ‎Krangle$‎. ‎In this paper we classify finite groups with planar graph‎. ‎...

The Common-Neighbourhood of a Graph

Abstract: The most widely used and well-known vulnerability measures of a connected graph are based on the neighbourhood concept. It takes into account neighbour-integrity, edge-integrity and accessibility number. In this work we define and examine common-neighbourhood of a connected graph as a new global connectivity measure. Our measure examines the neighbourhoods of all pairs of vertices of ...

The neighbourhood polynomial of a graph

We examine neighbourhood polynomials, which are generating functions for the number of faces of each cardinality in the neighbourhood complex of a graph. We provide explicit polynomials for hypercubes, for graphs not containing a four-cycle and for the graphs resulting from joins and Cartesian products. We also show that the closure of the roots are dense in the complex plane except possibly in...