English

Connecting hypercube 1-factors

Combinatorics 2025-08-22 v1

Abstract

A 1-factorisation of a regular graph GG is a partition of its edge set E(G)E(G) into perfect matchings of GG. Behague asked for the minimal r=r(d)r=r(d) such that some 11-factorisation of the dd-dimensional hypercube QdQ_d has the property that the union of any rr of its 1-factors is connected. Previous work by Laufer on perfect 11-factorisations implied that rr is at least three, and Behague gave a construction with r=d2+1r=\big\lceil\frac{d}{2}\big\rceil+1. We improve this upper bound, giving a random construction with r=O(logd)r=O(\log d). In other words, we prove the existence of a 1-factorisation M={M1,,Md}\mathcal{M} = \{M_1,\dotsc,M_d\} of the hypercube QdQ_d such that every NM\mathcal{N}\subseteq \mathcal{M} of size Ω(logd)\Omega(\log d) is such that N\bigcup \mathcal{N} is connected.

Keywords

Cite

@article{arxiv.2508.15698,
  title  = {Connecting hypercube 1-factors},
  author = {Lawrence Hollom and Benedict Randall Shaw},
  journal= {arXiv preprint arXiv:2508.15698},
  year   = {2025}
}

Comments

14 pages

R2 v1 2026-07-01T05:00:25.347Z