On the 1-2-3-conjecture

Akbar Davoodi (1) , Behnaz Omoomi (1)

1 Department of Mathematical Sciences [Isfahan]

A k-edge-weighting of a graph G is a function w:E(G)→{1,…,k}. An edge-weighting naturally induces a vertex coloring c, where for every vertex v∈V(G), c(v)=∑e∼vw(e). If the induced coloring c is a proper vertex coloring, then w is called a vertex-coloring k-edge-weighting (VC k-EW). Karoński et al. (J. Combin. Theory Ser. B, 91 (2004) 151 13;157) conjectured that every graph admits a VC 3-EW. This conjecture is known as the 1-2-3-conjecture. In this paper, first, we study the vertex-coloring edge-weighting of the Cartesian product of graphs. We prove that if the 1-2-3-conjecture holds for two graphs G and H, then it also holds for G□H. Also we prove that the Cartesian product of connected bipartite graphs admits a VC 2-EW. Moreover, we present several sufficient conditions for a graph to admit a VC 2-EW. Finally, we explore some bipartite graphs which do not admit a VC 2-EW.

Mots clés: Vertex-coloring edge-weighting; 1-2-3-conjecture; Edge weighting; Vertex-coloring 2-edge-weighting

Domaines: Mathématique discrète [cs.DM]; Interface homme-machine [cs.HC]

Akbar Davoodi, Behnaz Omoomi. On the 1-2-3-conjecture. Discrete Mathematics and Theoretical Computer Science, 2015, Vol. 17 no. 1 (1), pp.67--78. ⟨10.46298/dmtcs.2117⟩. ⟨hal-01196861⟩