English

On Ramsey numbers of 3-uniform Berge cycles

Combinatorics 2022-04-28 v1

Abstract

For an arbitrary graph GG, a hypergraph H\mathcal{H} is called Berge-GG if there is a bijection Φ:E(G)E(H)\Phi :E(G)\longrightarrow E( \mathcal{H}) such that for each eE(G)e\in E(G), we have eΦ(e)e\subseteq \Phi (e). We denote by BrG\mathcal{B}^rG, the family of rr-uniform Berge-GG hypergraphs. For families H1,H2,,Ht\mathcal{H}_1, \mathcal{H}_2,\ldots, \mathcal{H}_t of rr-uniform hypergraphs, the Ramsey number R(H1,H2,,Ht)R(\mathcal{H}_1, \mathcal{H}_2,\ldots, \mathcal{H}_t) is the smallest integer nn such that in every tt-hyperedge coloring of Knr\mathcal{K}_{n}^r there is a monochromatic copy of a hypergraph in Hi\mathcal{H}_i of color ii, for some 1it1\leq i\leq t. Recently, the Ramsey problems of Berge hypergraphs have been studied by many researchers. In this paper, we focus on Ramsey number involving 33-uniform Berge cycles and we prove that for n4n \geq 4, R(B3Cn,B3Cn,B3C3)=n+1. R(\mathcal{B}^3C_n,\mathcal{B}^3C_n,\mathcal{B}^3C_3)=n+1. Moreover, for mn6m \geq n\geq 6 and m11m\geq 11, we show that R(B3Km,B3Cn)=m+n121.R(\mathcal{B}^3K_m,\mathcal{B}^3C_n)= m+\lfloor \frac{n-1}{2}\rfloor -1. This is the first result of Ramsey number for two different families of Berge hypergraphs.

Keywords

Cite

@article{arxiv.2204.12840,
  title  = {On Ramsey numbers of 3-uniform Berge cycles},
  author = {Leila Maherani and Maryam Shahsiah},
  journal= {arXiv preprint arXiv:2204.12840},
  year   = {2022}
}