English

The Global Structure of a Typical Graph Without $H$ as an Induced Subgraph when $H$ is a Cycle

Combinatorics 2025-06-05 v1

Abstract

One way to certify that a graph does not contain an induced cycle of length six is to provide a partition of its vertex set into (i) a stable set, and (ii) a graph containing no stable set of size three and no induced matching of size two. We show that almost every graph which does not contain a cycle of length six as an induced subgraph has such a certificate. We obtain similar characterizations of the structure of almost all graphs which contain no induced cycle of length kk for all even kk exceeding six. (Similar results were obtained for k=3k=3 by Erdos, Kleitman, and Rothschild in 1976, for k=4,5k =4,5 by Promel and Steger in 1991 and for odd kk exceeding 5 by Balogh and Butterfield in 2009.) We prove that a simiiar theorem for all HH holds up to the deletion of a set of o(V(G))o(|V(G)|) vertices and ask for which HH the characterization holds fully.

Keywords

Cite

@article{arxiv.2506.03544,
  title  = {The Global Structure of a Typical Graph Without $H$ as an Induced Subgraph when $H$ is a Cycle},
  author = {Bruce Reed},
  journal= {arXiv preprint arXiv:2506.03544},
  year   = {2025}
}