English

The Ramsey number of a long cycle and complete graphs

Combinatorics 2020-09-28 v2

Abstract

In this paper, we prove that the multicolored Ramsey number R(G1,,Gn,Kn1,,Knr)R(G_1,\dots,G_n,K_{n_1},\dots,K_{n_r}) is at least (γ1)(κ1)+1(\gamma-1)(\kappa-1)+1 for arbitrary connected graphs G1,,GnG_1,\dots,G_n and n1,,nrNn_1,\dots,n_r\in\mathbb{N}, where γ=R(G1,,Gn)\gamma=R(G_1,\dots,G_n) and κ=R(Kn1,,Knr)\kappa=R(K_{n_1},\dots,K_{n_r}). Erd\H os at al. conjectured that R(Cn,Kl)=(n1)(l1)+1R(C_n,K_l)=(n-1)(l-1)+1 for every nl3n\geq l\geq 3 except for n=l=3n=l=3. Nikiforov proved this conjecture for n4l+2n\geq 4l+2. Using the above bound, we derive the following generalization of this result. R(Cn,Kn1,,Knr)=(n1)(κ1)+1R(C_n,K_{n_1},\dots,K_{n_r})=(n-1)(\kappa-1)+1, where κ=R(Kn1,,Knr)\kappa=R(K_{n_1},\dots,K_{n_r}) and n4κ+2n\geq 4\kappa+2.

Keywords

Cite

@article{arxiv.2003.12691,
  title  = {The Ramsey number of a long cycle and complete graphs},
  author = {Péter Madarasi},
  journal= {arXiv preprint arXiv:2003.12691},
  year   = {2020}
}