2010/03/11 by Jan Ekstein, Ekstein, Jan, Jiří Fiala +5 · 1 citation
Computer Science · #Discrete Mathematics (cs.DM) #FOS: Computer and information sciences #G.2.2 #cs.DM
paper · pdf · doi:10.48550/arxiv.1003.2291
3 pages
arxiv created 2010/03/11 · arxiv updated 2010/03/12
The packing chromatic number χρ(G) of a graph G is the smallest integer k such that the vertex set V(G) can be partitioned into disjoint classes X1, ..., Xk, where vertices in Xi have pairwise distance greater than i. For the 2-dimensional square lattice ℤ2 it is proved that χρ(ℤ2) ≥ 12, which improves the previously known lower bound 10.