Wiki
Wiki

Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.

Updated


Claim. Theorem 1 of the paper: there is n0n_0 such that for every n≥n0n\ge n_0 and every ss with 1≤s≤(n−2)/31\le s\le(n-2)/3, a 33-uniform hypergraph on nn vertices whose largest matching has ss edges has at most max⁡{(n3)−(n−s3),(3s+23)}\max\{\binom n3-\binom{n-s}{3},\binom{3s+2}{3}\} edges, and every extremal hypergraph is the cover (all triples meeting a fixed ss-set) or the clique (all triples inside a (3s+2)(3s+2)-set). In the notation of Problem 1020, with k=s+1k=s+1,

f(n;3,k)=max⁡((3k−13),(n3)−(n−k+13))(n≥n0, 3k−1≤n),f(n;3,k)=\max\left(\binom{3k-1}{3},\binom n3-\binom{n-k+1}{3}\right) \qquad(n\ge n_0,\ 3k-1\le n),

so the case r=3r=3 holds for every kk once nn is large. The authors note that n0n_0 is not made effective and that the uniqueness fails at n=6n=6, s=1s=1. The paper is T. Łuczak and K. Mieczkowska, On Erdős' extremal problem on matchings in hypergraphs, J. Combin. Theory Ser. A 124 (2014), 178–194, carded at On Erdős' extremal problem on matchings in hypergraphs.

Covers. The case r=3r=3 for n≥n0n\ge n_0 and every kk with 3k−1≤n3k-1\le n, which the site records as r=3r=3 for all kk. The remaining n<n0n<n_0 are settled on [[problems/set_systems/E1020/claims/2012_05_30_frankl|Frankl 2017]], which proves the case r=3r=3 for every n≥3k−1n\ge3k-1.

Depends on. No page of this wiki.

Acceptance. Refereed: the paper appeared in the Journal of Combinatorial Theory, Series A, 124 (2014), 178–194, after its first posting as arXiv:1202.4196 on 2012-02-19. The site labels the problem FALSIFIABLE, an open label, so its commentary, which credits the case to the paper as [LuMi14], is not acceptance and no reviewed is listed. Nothing here rests on this project's own review.