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Ramsey numbers of long even cycles versus books

Combinatorics 2025-10-01 v1

Abstract

For any positive integers kk and nn, let Bn(k)B_n^{(k)} be the book graph consisting of nn copies of the complete graph Kk+1K_{k+1} sharing a common KkK_k. Let CmC_m be a cycle of length mm. Prior work by Allen, \L uczak, Polcyn, and Zhang (2023) established the Ramsey number R(Cm,Bn(1))R(C_{m},B_n^{(1)}) for all sufficiently large even integer m=Ω(n9/10)m = \Omega(n^{9/10}). Recently, Hu, Lin, {\L}uczak, Ning, and Peng (2025) obtained the exact value of R(Cm,Bn(2))R(C_{m},B_n^{(2)}) under the same asymptotic conditions. A natural problem is to determine the exact value of R(Cm,Bn(k))R(C_{m},B_n^{(k)}) for each fixed k3k\ge3 under similar conditions. This paper provides a complete solution to this problem. The lower bound is proved by an explicit construction, while the tight upper bound is established by analyzing the corresponding Ramsey graph using semi-random ideas.

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Cite

@article{arxiv.2509.26323,
  title  = {Ramsey numbers of long even cycles versus books},
  author = {Qizhong Lin and Shixi Song},
  journal= {arXiv preprint arXiv:2509.26323},
  year   = {2025}
}

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18 pages