English

Graphs with no induced $K_{2,t}$

Combinatorics 2021-02-03 v2

Abstract

Consider a graph GG on nn vertices with α(n2)\alpha \binom{n}{2} edges which does not contain an induced K2,tK_{2, t} (t2t \geqslant 2). How large does α\alpha have to be to ensure that GG contains, say, a large clique or some fixed subgraph HH? We give results for two regimes: for α\alpha bounded away from zero and for α=o(1)\alpha = o(1). Our results for α=o(1)\alpha = o(1) are strongly related to the Induced Tur\'{a}n numbers which were recently introduced by Loh, Tait, Timmons and Zhou. For α\alpha bounded away from zero, our results can be seen as a generalisation of a result of Gy\'{a}rf\'{a}s, Hubenko and Solymosi and more recently Holmsen (whose argument inspired ours).

Keywords

Cite

@article{arxiv.1912.07970,
  title  = {Graphs with no induced $K_{2,t}$},
  author = {Freddie Illingworth},
  journal= {arXiv preprint arXiv:1912.07970},
  year   = {2021}
}

Comments

8 pages; final version incorporating changes suggested by referees; new result in last section

R2 v1 2026-06-23T12:48:22.068Z