English

A positive instance of Scott's Conjecture on induced subdivisions

Combinatorics 2026-02-13 v1

Abstract

For a graph GG, χ(G)\chi(G) denotes the chromatic number of GG and ω(G)\omega(G) denotes the size of the largest clique in GG. A hereditary class of graphs is called χ\chi-bounded if there is a function ff such that for each graph GG in the class, χ(G)f(ω(G))\chi(G) \le f(\omega(G)). Scott (1997) conjectured that for every graph HH, the class of graphs which do not contain any subdivision of HH as an induced subgraph is χ\chi-bounded. He proved his conjecture when HH is a tree and when HH is the complete graph on four vertices, K4K_4. Esperet and Trotignon (2019) proved that the conjecture holds when HH is K4K_4 with one edge subdivided once. Scott's conjecture was disproved by Pawlik et al. (2014). Chalopin et al. (2016) gave more counterexamples including the graph obtained from K4K_4 by subdividing each edge of a 4-cycle once. We prove that the conjecture holds when HH consists of a complete bipartite graph with and additional vertex which has exactly two neighbours, on the same side of the bipartition. As a special case, this proves Scott's conjecture when HH is obtained from K4K_4 by subdividing two disjoint edges.

Keywords

Cite

@article{arxiv.2602.11990,
  title  = {A positive instance of Scott's Conjecture on induced subdivisions},
  author = {Kathie Cameron and Ni Luh Dewi Sintiari and Sophie Spirkl},
  journal= {arXiv preprint arXiv:2602.11990},
  year   = {2026}
}