English

Hypergraphs not containing a tight tree with a bounded trunk ~II: 3-trees with a trunk of size 2

Combinatorics 2019-02-04 v2

Abstract

A tight rr-tree TT is an rr-uniform hypergraph that has an edge-ordering e1,e2,,ete_1, e_2, \dots, e_t such that for each i2i\geq 2, eie_i has a vertex viv_i that does not belong to any previous edge and eivie_i-v_i is contained in eje_j for some j<ij<i. Kalai conjectured in 1984 that every nn-vertex rr-uniform hypergraph with more than t1r(nr1)\frac{t-1}{r}\binom{n}{r-1} edges contains every tight rr-tree TT with tt edges. A trunk TT' of a tight rr-tree TT is a tight subtree TT' of TT such that vertices in V(T)V(T)V(T)\setminus V(T') are leaves in TT. Kalai's Conjecture was proved in 1987 for tight rr-trees that have a trunk of size one. In a previous paper we proved an asymptotic version of Kalai's Conjecture for all tight rr-trees that have a trunk of bounded size. In this paper we continue that work to establish the exact form of Kalai's Conjecture for all tight 33-trees with at least 2020 edges that have a trunk of size two.

Keywords

Cite

@article{arxiv.1807.07057,
  title  = {Hypergraphs not containing a tight tree with a bounded trunk ~II: 3-trees with a trunk of size 2},
  author = {Zoltán Füredi and Tao Jiang and Alexandr Kostochka and Dhruv Mubayi and Jacques Verstraëte},
  journal= {arXiv preprint arXiv:1807.07057},
  year   = {2019}
}

Comments

12 pages. Same as the first version. Only metadata has been changed