Proper Connection Of Direct Products

Abstract

The proper connection number of a graph is the least integer k for which the graph has an edge coloring with k colors, with the property that any two vertices are joined by a properly colored path. We prove that given two connected non-bipartite graphs, one of which is (vertex) 2-connected, the proper connection number of their direct product is 2.

Keywords

• direct product of graphs
• proper connection of graphs.