The extended irregular domination problem

Abstract

In this paper we introduce a new domination problem strongly related to the following one recently proposed by Broe, Chartrand and Zhang. One says that a vertex $v$ of a graph $\Gamma$ labeled with an integer $\ell$ dominates the vertices of $\Gamma$ having distance $\ell$ from $v$. An irregular dominating set of a given graph $\Gamma$ is a set $S$ of vertices of $\Gamma$, having distinct positive labels, whose elements dominate every vertex of $\Gamma$. Since it has been proven that no connected vertex transitive graph admits an irregular dominating set, here we introduce the concept of an extended irregular dominating set, where we admit that precisely one vertex, labeled with 0, dominates itself. Then we present existence or non existence results of an extended irregular dominating set $S$ for several classes of graphs, focusing in particular on the case in which $S$ is as small as possible. We also propose two conjectures.