English

Approximate Steiner $(r-1,r,n)$-systems without $3$ blocks on $r+2$ points

Combinatorics 2019-12-17 v4

Abstract

For a family F{\mathcal F} of rr-graphs, let ex(n,F)\mathrm{ex}(n,{\mathcal F}) denote the maximum number of edges in an F{\mathcal F}-free rr-graph on nn vertices. Let Fr(v,e){\mathcal F}_r(v,e) denote the family of all rr-graphs with ee edges and at most vv vertices. We prove that ex(n,Fr(r+1,2)Fr(r+2,3))=(1ro(1))(nr1)\mathrm{ex}(n,{\mathcal F}_r(r+1,2) \cup {\mathcal F}_r(r+2,3)) = (\frac{1}{r} - o(1)) \binom{n}{r-1}.

Keywords

Cite

@article{arxiv.1907.08084,
  title  = {Approximate Steiner $(r-1,r,n)$-systems without $3$ blocks on $r+2$ points},
  author = {Alexander Sidorenko},
  journal= {arXiv preprint arXiv:1907.08084},
  year   = {2019}
}

Comments

Final version with the changes suggested by the referees. To appear in "Journal of Combinatorial Designs"

R2 v1 2026-06-23T10:24:24.451Z