English

Further progress on Wojda's conjecture

Combinatorics 2026-01-21 v1

Abstract

Two digraphs of order nn are said to pack if they can be found as edge-disjoint subgraphs of the complete digraph of order nn. It is well established that if the sum of the sizes of the two digraphs is at most 2n22n-2, then they pack, with this bound being sharp. However, it is sufficient for the size of the smaller digraph to be only slightly below nn for the sum of their sizes to significantly exceed this threshold while still guaranteeing the existence of a packing. In 1985, Wojda conjectured that for any 2mn/22 \leq m \leq n/2, if one digraph has size at most nmn - m and the other has size less than 2nn/m2n - \lfloor n/m \rfloor, then the two digraphs pack. It was previously known that this conjecture holds for m=Ω(n)m = \Omega(\sqrt{n}). In this paper, we confirm it for m93m \geq 93 and n31mn \geq 31m.

Keywords

Cite

@article{arxiv.2601.13085,
  title  = {Further progress on Wojda's conjecture},
  author = {Maciej Cisiński and Andrzej Żak},
  journal= {arXiv preprint arXiv:2601.13085},
  year   = {2026}
}
R2 v1 2026-07-01T09:10:39.787Z