English

Packing list-colourings

Combinatorics 2023-08-03 v2 Discrete Mathematics

Abstract

List colouring is an influential and classic topic in graph theory. We initiate the study of a natural strengthening of this problem, where instead of one list-colouring, we seek many in parallel. Our explorations have uncovered a potentially rich seam of interesting problems spanning chromatic graph theory. Given a kk-list-assignment LL of a graph GG, which is the assignment of a list L(v)L(v) of kk colours to each vertex vV(G)v\in V(G), we study the existence of kk pairwise-disjoint proper colourings of GG using colours from these lists. We may refer to this as a \emph{list-packing}. Using a mix of combinatorial and probabilistic methods, we set out some basic upper bounds on the smallest kk for which such a list-packing is always guaranteed, in terms of the number of vertices, the degeneracy, the maximum degree, or the (list) chromatic number of GG. (The reader might already find it interesting that such a minimal kk is well defined.) We also pursue a more focused study of the case when GG is a bipartite graph. Our results do not yet rule out the tantalising prospect that the minimal kk above is not too much larger than the list chromatic number. Our study has taken inspiration from study of the strong chromatic number, and we also explore generalisations of the problem above in the same spirit.

Keywords

Cite

@article{arxiv.2110.05230,
  title  = {Packing list-colourings},
  author = {Stijn Cambie and Wouter Cames van Batenburg and Ewan Davies and Ross J. Kang},
  journal= {arXiv preprint arXiv:2110.05230},
  year   = {2023}
}

Comments

32 pages, 2 tables; v2 accepted to Random Structures & Algorithms

R2 v1 2026-06-24T06:47:29.784Z