English

Multicolor Ramsey numbers on stars versus pat

Combinatorics 2023-08-22 v1

Abstract

For given simple graphs H1,H2,,HcH_1,H_2,\dots,H_c, the multicolor Ramsey number R(H1,H2,,Hc)R(H_1,H_2,\dots,H_c) is defined as the smallest positive integer nn such that for an arbitrary edge-decomposition {Gi}i=1c\{G_i\}^c_{i=1} of the complete graph KnK_n, at least one GiG_i has a subgraph isomorphic to HiH_i. Let m,n1,n2,,ncm,n_1,n_2,\dots,n_c be positive integers and Σ=i=1c(ni1)\Sigma=\sum_{i=1}^{c}(n_i-1). Some bounds and exact values of R(K1,n1,,K1,nc,Pm)R(K_{1,n_1},\dots,K_{1,n_c},P_m) have been obtained in literature. Wang (Graphs Combin., 2020) conjectured that if Σ≢0(modm1)\Sigma\not\equiv 0\pmod{m-1} and Σ+1(m3)2\Sigma+1\ge (m-3)^2, then R(K1,n1,,K1,nc,Pm)=Σ+m1.R(K_{1,n_1},\ldots, K_{1,n_c}, P_m)=\Sigma+m-1. In this note, we give a new lower bound and some exact values of R(K1,n1,,K1,nc,Pm)R(K_{1,n_1},\dots,K_{1,n_c},P_m) when mΣm\leq\Sigma, Σk(modm1)\Sigma\equiv k\pmod{m-1}, and 2km22\leq k \leq m-2. These results partially confirm Wang's conjecture.

Keywords

Cite

@article{arxiv.2308.09950,
  title  = {Multicolor Ramsey numbers on stars versus pat},
  author = {Xuejun Zhang and Xinmin Hou},
  journal= {arXiv preprint arXiv:2308.09950},
  year   = {2023}
}

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6 pages