Strong orientation of a connected graph for a crossing family
Given a connected graph $G=(V,E)$ and a crossing family $\mathcal{C}$ over ground set $V$ such that $|\delta_G(U)|\geq 2$ for every $U\in \mathcal{C}$, we prove there exists a strong orientation of $G$ for $\mathcal{C}$, i.e., an orientation of $G$ such that each set in $\mathcal{C}$ has at least on...
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Zusammenfassung: | Given a connected graph $G=(V,E)$ and a crossing family $\mathcal{C}$ over
ground set $V$ such that $|\delta_G(U)|\geq 2$ for every $U\in \mathcal{C}$, we
prove there exists a strong orientation of $G$ for $\mathcal{C}$, i.e., an
orientation of $G$ such that each set in $\mathcal{C}$ 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 $2$, the arcs
of nonzero weight must be disconnected. |
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DOI: | 10.48550/arxiv.2411.13202 |