On outer-connected domination for graph products

An outer-connected dominating set for an arbitrary graph $G$ is a set $\tilde{D}\subseteq V$ such that $\tilde{D}$ is a dominating set and the induced subgraph $G[V\setminus \tilde{D}]$ be connected. In this paper, we focus on the outer-connected domination number of the product of graphs. We investigate the existence of outer-connected dominating set in lexicographic product and Corona of two arbitrary graphs, and we present upper bounds for outer-connected domination number in lexicographic and Cartesian product of graphs. Also, we establish an equivalent form of the Vizing’s conjecture for outer-connected domination number in lexicographic and Cartesian product as $\tilde{\gamma_c}(G \circ K)\tilde{\gamma_c}(H \circ K) \leq \tilde{\gamma_c}(G\Box H)\circ K$. Furthermore, we study the outer-connected domination number of the direct product of finitely many complete graphs.