English

A container theorem for general digraphs with forbidden subdigraphs

Combinatorics 2026-05-20 v2

Abstract

In a seminal work, K\"uhn, Osthus, Townsend, and Zhao used the hypergraph container method to determine the typical structure of oriented graphs and digraphs avoiding a fixed tournament or cycle. Their main tool, a container theorem for oriented graphs, does not directly extend to all digraphs due to the existence of counterexamples such as the double triangle DK3DK_3. In this paper we prove a container theorem for general digraphs under a natural sparsity condition. For the edge-weight parameter a=2a=2, this condition permits digraphs with 22-cycles (density at most 11) but excludes denser obstructions like DK3DK_3; for larger aa it allows digraphs with a controlled density of 22-cycles. As applications, we obtain asymptotic counting results for HH-free digraphs and describe the typical structure of digraphs avoiding a fixed digraph HH satisfying our condition. Our results unify and extend several previous results in the area.

Keywords

Cite

@article{arxiv.2603.18542,
  title  = {A container theorem for general digraphs with forbidden subdigraphs},
  author = {Meili Liang and Yue Guan and Ruiling Zheng and Jianxi Liu},
  journal= {arXiv preprint arXiv:2603.18542},
  year   = {2026}
}
R2 v1 2026-07-01T11:27:32.993Z