Packing coloring of hypercubes with extended Hamming codes

A {\em packing coloring} of a graph \(G\) is a mapping assigning a positive integer (a color) to every vertex of \(G\) such that every two vertices of color \(k\) are at distance at least \(k+1\). The least number of colors needed for a packing coloring of \(G\) is called the {\em packing chromatic number} of \(G\). In this paper, we continue the study of the packing chromatic number of hypercubes and we improve the upper bounds reported by Torres and Valencia-Pabon ({\em P. Torres, M. Valencia-Pabon, The packing chromatic number of hypercubes, Discrete Appl. Math. 190--191 (2015), 127--140}) by presenting recursive constructions of subsets of distant vertices making use of the properties of the extended Hamming codes. We also answer in negative a question on packing coloring of Cartesian products raised by Brešar, Klavžar, and Rall ({\em Problem 5, Brešar et al., On the packing chromatic number of Cartesian products, hexagonal lattice, and trees. Discrete Appl. Math. 155 (2007), 2303--2311.}).