English

A counterexample regarding labelled well-quasi-ordering

Combinatorics 2018-10-08 v3

Abstract

Korpelainen, Lozin, and Razgon conjectured that a hereditary property of graphs which is well-quasi-ordered by the induced subgraph order and defined by only finitely many minimal forbidden induced subgraphs is labelled well-quasi-ordered, a notion stronger than that of nn-well-quasi-order introduced by Pouzet in the 1970s. We present a counterexample to this conjecture. In fact, we exhibit a hereditary property of graphs which is well-quasi-ordered by the induced subgraph order and defined by finitely many minimal forbidden induced subgraphs yet is not 22-well-quasi-ordered. This counterexample is based on the widdershins spiral, which has received some study in the area of permutation patterns.

Keywords

Cite

@article{arxiv.1709.10042,
  title  = {A counterexample regarding labelled well-quasi-ordering},
  author = {Robert Brignall and Michael Engen and Vincent Vatter},
  journal= {arXiv preprint arXiv:1709.10042},
  year   = {2018}
}
R2 v1 2026-06-22T21:58:00.985Z