English

Almost all $C_k$-free oriented graphs have $\Theta(n)$ backwards edges

Combinatorics 2026-03-20 v1

Abstract

We prove a conjecture of K\"uhn, Osthus, Townsend and Zhao \cite{kuhn2017structure} stating that almost every CkC_k-free oriented graph on nn vertices has Θ(n)\Theta(n) backwards edges in a transitive-optimal ordering. The same holds for CkC_k-free digraphs when kk is even. Our proof combines the hypergraph container method with a stability analysis and an inductive counting argument. As a byproduct, we also determine the typical structure of oriented graphs and digraphs that avoid the blow-up CktC_{k}^t, extending the main result of \cite{kuhn2017structure} to the blown-up setting.

Keywords

Cite

@article{arxiv.2603.18553,
  title  = {Almost all $C_k$-free oriented graphs have $\Theta(n)$ backwards edges},
  author = {Jianxi Liu and Meili Liang},
  journal= {arXiv preprint arXiv:2603.18553},
  year   = {2026}
}
R2 v1 2026-07-01T11:27:33.845Z