Proper connection number and graph products

Abstract

A path $P$ in an edge-colored graph $G$ is called \emph{a proper path} if no two adjacent edges of $P$ are colored the same, and $G$ is \emph{proper connected} if every two vertices of $G$ are connected by a proper path in $G$. The \emph{proper connection number} of a connected graph $G$, denoted by $pc(G)$, is the minimum number of colors that are needed to make $G$ proper connected. In this paper, we study the proper connection number on the lexicographical, strong, Cartesian, and direct product and present several upper bounds for these products of graphs.

16 pages, 2 figures. arXiv admin note: text overlap with arXiv:1505.01424. text overlap with arXiv:1504.02414 by other authors