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 -free oriented graph on vertices has backwards edges in a transitive-optimal ordering. The same holds for -free digraphs when 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 , 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}
}