English

Rainbow odd cycles

Combinatorics 2021-10-13 v3

Abstract

We prove that every family of (not necessarily distinct) odd cycles O1,,O2n/21O_1, \dots, O_{2\lceil n/2 \rceil-1} in the complete graph KnK_n on nn vertices has a rainbow odd cycle (that is, a set of edges from distinct OiO_i's, forming an odd cycle). As part of the proof, we characterize those families of nn odd cycles in Kn+1K_{n+1} that do not have any rainbow odd cycle. We also characterize those families of nn cycles in Kn+1K_{n+1}, as well as those of nn edge-disjoint nonempty subgraphs of Kn+1K_{n+1}, without any rainbow cycle.

Keywords

Cite

@article{arxiv.2007.09719,
  title  = {Rainbow odd cycles},
  author = {Ron Aharoni and Joseph Briggs and Ron Holzman and Zilin Jiang},
  journal= {arXiv preprint arXiv:2007.09719},
  year   = {2021}
}

Comments

14 pages, 2 figures, accepted to SIAM Journal on Discrete Mathematics (SIDMA)

R2 v1 2026-06-23T17:13:46.316Z