English

The degree and codegree threshold for generalized triangle and some trees covering

Combinatorics 2023-07-06 v1

Abstract

Given two kk-uniform hypergraphs FF and GG, we say that GG has an FF-covering if for every vertex in GG there is a copy of FF covering it. For 1ik11\leq i\leq k-1, the minimum ii-degree δi(G)\delta_i(G) of GG is the minimum integer such that every ii vertices are contained in at least δi(G)\delta_i(G) edges. Let ci(n,F)c_i(n,F) be the largest minimum ii-degree among all nn-vertex kk-uniform hypergraphs that have no FF-covering. In this paper, we consider the FF-covering problem in 33-uniform hypergraphs when FF is the generalized triangle TT, where TT is a 33-uniform hypergraph with the vertex set {v1,v2,v3,v4,v5}\{v_1,v_2,v_3,v_4,v_5\} and the edge set {{v1v2v3},{v1v2v4},{v3v4v5}}\{\{v_{1}v_{2}v_{3}\},\{v_{1}v_{2}v_{4}\},\{v_{3}v_{4}v_{5}\}\}. We give the exact value of c2(n,T)c_2(n,T) and asymptotically determine c1(n,T)c_1(n,T). We also consider the FF-covering problem in 33-uniform hypergraphs when FF are some trees, such as the linear kk-path PkP_k and the star SkS_k. Especially, we provide bounds of ci(n,Pk)c_i(n,P_k) and ci(n,Sk)c_i(n,S_k) for k3k\geq 3, where i=1,2i=1,2.

Keywords

Cite

@article{arxiv.2307.01647,
  title  = {The degree and codegree threshold for generalized triangle and some trees covering},
  author = {Ran Gu and Shuaichao Wang},
  journal= {arXiv preprint arXiv:2307.01647},
  year   = {2023}
}
R2 v1 2026-06-28T11:21:45.505Z