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A note on tree-cycle Ramsey numbers

Combinatorics 2026-07-20 v1

Abstract

Let R(Tn,Cm)R(T_n,C_m) denote the Ramsey number of a tree TnT_n on nn vertices versus a cycle CmC_m of length mm. Burr, Erd\H{o}s, Faudree, Rousseau, and Schelp (1982) asked for the least function f(m)f(m) such that R(Tn,Cm)=2n1R(T_n,C_m)=2n-1 for every odd m3m\ge 3 whenever nf(m)n\ge f(m). They proved that f(m)756m10f(m)\le 756m^{10}. This bound was later improved to 25m25m by Brennan (2016) and to 4m84m-8 by Fan and Lin (2025). In this note, we show that f(m)2m4f(m)\le 2m-4 by using a different method and conjecture that f(m)=(2m1)/3f(m)=\lceil (2m-1)/3\rceil.

Cite

@article{arxiv.2607.17831,
  title  = {A note on tree-cycle Ramsey numbers},
  author = {Ting Huang and Yanbo Zhang and Yaojun Chen},
  journal= {arXiv preprint arXiv:2607.17831},
  year   = {2026}
}

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6 pages