English

Anti-Ramsey number of matchings in $3$-uniform hypergraphs

Combinatorics 2023-05-26 v1

Abstract

Let n,s,n,s, and kk be positive integers such that k3k\geq 3, s3s\geq 3 and nksn\geq ks. An ss-matching MsM_s in a kk-uniform hypergraph is a set of ss pairwise disjoint edges. The anti-Ramsey number ar(n,k,Ms)\textrm{ar}(n,k,M_s) of an ss-matching is the smallest integer cc such that each edge-coloring of the nn-vertex kk-uniform complete hypergraph with exactly cc colors contains an ss-matching with distinct colors. In 2013, \"Ozkahya and Young proposed a conjecture on the exact value of ar(n,k,Ms)(n,k,M_s) for all nskn \geq sk and k3k \geq 3. A 2019 result by Frankl and Kupavskii verified this conjecture for all nsk+(s1)(k1)n \geq sk+(s-1)(k-1) and k3k \geq 3. We aim to determine the value of ar(n,3,Ms)(n,3,M_s) for 3sn<5s23s \leq n < 5s-2 in this paper. Namely, we prove that if 3s<n<5s23s<n<5s-2 and nn is large enough, then ar(n,3,Ms)=ex(n,3,Ms1)+2(n,3,M_s)=\textrm{ex}(n,3,M_{s-1})+2. Here ex(n,3,Ms1)\textrm{ex}(n,3,M_{s-1}) is the Tur\'an number of an (s1)(s-1)-matching. Thus this result confirms the conjecture of \"Ozkahya and Young for k=3k=3, 3s<n<5s23s<n<5s-2 and sufficiently large nn. For n=ksn=ks and k3k\geq 3, we present a new construction for the lower bound of ar(n,k,Ms)\textrm{ar}(n,k,M_{s}) which shows the conjecture by \"Ozkahya and Young is not true. In particular, for n=3sn=3s, we prove that ar(n,3,Ms)=ex(n,3,Ms1)+5\textrm{ar}(n,3,M_s)=\textrm{ex}(n,3,M_{s-1})+5 for sufficiently large nn.

Keywords

Cite

@article{arxiv.2305.15631,
  title  = {Anti-Ramsey number of matchings in $3$-uniform hypergraphs},
  author = {Mingyang Guo and Hongliang Lu and Xing Peng},
  journal= {arXiv preprint arXiv:2305.15631},
  year   = {2023}
}

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21 pages