On randomly generated intersecting hypergraphs II

Abstract

Let $c$ be a positive constant. Suppose that $r=o(n^{5/12})$ and the members of $\left(\genfrac{}{}{0ex}{}{[n]}{r}\right)$ are chosen sequentially at random to form an intersecting hypergraph $\mathcal{H}$. We show that whp $\mathcal{H}$ consists of a simple hypergraph $\mathcal{S}$ of size $\Theta (r/n^{1/3})$, a distinguished vertex $v$ and all $r$-sets which contain $v$ and meet every edge of $\mathcal{S}$. This is a continuation of the study of such random intersecting systems started in [Electron. J. Combin, (2003) R29] where the case $r=O(n^{1/3})$ was considered. To obtain the stated result we continue to investigate this question in the range $\omega (n^{1/3})\le r\le o(n^{5/12})$.

20 pages