English

On 1-subdivisions of transitive tournaments

Combinatorics 2022-05-06 v2

Abstract

The oriented Ramsey number r(H)\vec{r}(H) for an acyclic digraph HH is the minimum integer nn such that any nn-vertex tournament contains a copy of HH as a subgraph. We prove that the 11-subdivision of the kk-vertex transitive tournament HkH_k satisfies r(Hk)=O(k2loglogk)\vec{r}(H_k)= O(k^2\log\log k). This is tight up to multiplicative loglogk\log\log k-term. We also show that if TT is an nn-vertex tournament with Δ+(T)δ+(T)=O(n/k)k2\Delta^+(T)-\delta^+(T)= O(n/k) - k^2, then TT contains a 11-subdivision of Kk\vec{K}_k, a complete kk-vertex digraph with all possible k(k1)k(k-1) arcs. This is also tight up to multiplicative constant.

Keywords

Cite

@article{arxiv.2110.05002,
  title  = {On 1-subdivisions of transitive tournaments},
  author = {Jaehoon Kim and Hyunwoo Lee and Jaehyeon Seo},
  journal= {arXiv preprint arXiv:2110.05002},
  year   = {2022}
}