The Cost of Edge-distinguishing of the Cartesian Product of Connected Graphs

Abstract

A graph $G$ is said to be $d$-distinguishable if there is a vertex coloring of $G$ with a set of $d$ colors which breaks all of the automorphisms of $G$ but the identity. We call the minimum $d$ for which a graph $G$ is $d$-distinguishiable the distinguishing number of $G$, denoted by $D(G)$. When $D(G)=2$, the minimum number of vertices in one of the color classes is called the cost of distinguishing of $G$ and is shown by $\rho(G)$. In this paper, we generalize this concept to edge-coloring by introducing the cost of edge-distinguishing of a graph $G$, denoted by $\rho'(G)$. Then, we consider $\rho'(K_n )$ for $n\geq 6$ by finding a procedure that gives the minimum number of edges of $K_n$ that should be colored differently to have a $2$-distinguishing edge-coloring. Afterwards, we develop a machinery to state a sufficient condition for a coloring of the Cartesian product to break all non-trivial automorphisms. Using this sufficient condition, we determine when cost of distinguishing and edge-distinguishing of the Cartesian power of a path equals to one. We also show that this parameters are equal to one for any Cartesian product of finitely many paths of different lengths. Moreover, we do a similar work for the Cartesian powers of a cycle and also for the Cartesian products of finitely many cycles of different orders. Upper bounds for the cost of edge-distinguishing of hypercubes and the Cartesian powers of complete graphs are also presented.