Independent transversal domination number of a graph

Abstract

Let $G=(V,E)$ be a graph. A set $S\subseteq V(G)$ is a {\it dominating set} of $G$ if every vertex in $V\setminus S$ is adjacent to a vertex of $S$. The {\it domination number} of $G$, denoted by $\gamma (G)$, is the cardinality of a minimum dominating set of $G$. Furthermore, a dominating set $S$ is an {\it independent transversal dominating set} of $G$ if it intersects every maximum independent set of $G$. The {\it independent transversal domination number} of $G$, denoted by ${\gamma }_{it}(G)$, is the cardinality of a minimum independent transversal dominating set of $G$. In 2012, Hamid initiated the study of the independent transversal domination of graphs, and posed the following two conjectures: Conjecture 1. If $G$ is a non-complete connected graph on $n$ vertices, then ${\gamma }_{it}(G)\le \lceil \frac{n}{2}\rceil$. Conjecture 2. If G is a connected bipartite graph, then ${\gamma }_{it}(G)$ is either $\gamma (G)$ or $\gamma (G)+1$. We show that Conjecture 1 is not true in general. Very recently, Conjecture 2 is partially verified to be true by Ahangar, Samodivkin, Yero. Here, we prove the full statement of Conjecture 2. In addition, we give a correct version of a theorem of Hamid. Finally, we answer a problem posed by Martínez, Almira, and Yero on the independent transversal total domination of a graph.

9 pages