English

Bounded degree graphs and hypergraphs with no full rainbow matchings

Combinatorics 2025-12-19 v2

Abstract

Given a multi-hypergraph GG that is edge-colored into color classes E1,,EnE_1, \ldots, E_n, a full rainbow matching is a matching of GG that contains exactly one edge from each color class EiE_i. One way to guarantee the existence of a full rainbow matching is to have the size of each color class EiE_i be sufficiently large compared to the maximum degree of GG. In this paper, we apply a simple iterative method to construct edge-colored multi-hypergraphs with a given maximum degree, large color classes, and no full rainbow matchings. First, for every r1r \ge 1 and Δ2\Delta \ge 2, we construct edge-colored rr-uniform multi-hypergraphs with maximum degree Δ\Delta such that each color class has size EirΔ1|E_i| \ge r\Delta - 1 and there is no full rainbow matching, which demonstrates that a theorem of Aharoni, Berger, and Meshulam (2005) is best possible. Second, we construct properly edge-colored multigraphs with no full rainbow matchings which disprove conjectures of Delcourt and Postle (2022). Finally, we apply results on full rainbow matchings to list edge-colorings and prove that a color degree generalization of Galvin's theorem (1995) does not hold.

Keywords

Cite

@article{arxiv.2401.06029,
  title  = {Bounded degree graphs and hypergraphs with no full rainbow matchings},
  author = {Ronen Wdowinski},
  journal= {arXiv preprint arXiv:2401.06029},
  year   = {2025}
}
R2 v1 2026-06-28T14:14:26.897Z