English

Strong orientation of a connected graph for a crossing family

Combinatorics 2024-11-21 v1

Abstract

Given a connected graph G=(V,E)G=(V,E) and a crossing family C\mathcal{C} over ground set VV such that δG(U)2|\delta_G(U)|\geq 2 for every UCU\in \mathcal{C}, we prove there exists a strong orientation of GG for C\mathcal{C}, i.e., an orientation of GG such that each set in C\mathcal{C} has at least one outgoing and at least one incoming arc. This implies the main conjecture in Chudnovsky et al. (Disjoint dijoins. Journal of Combinatorial Theory, Series B, 120:18--35, 2016). In particular, in every minimal counterexample to the Edmonds-Giles conjecture where the minimum weight of a dicut is 22, the arcs of nonzero weight must be disconnected.

Keywords

Cite

@article{arxiv.2411.13202,
  title  = {Strong orientation of a connected graph for a crossing family},
  author = {Ahmad Abdi and Mahsa Dalirrooyfard and Meike Neuwohner},
  journal= {arXiv preprint arXiv:2411.13202},
  year   = {2024}
}

Comments

10 pages, 2 figures