Generalized laminar families and certain forbidden matrices
Abstract
Recall that in a laminar family, any two sets are either disjoint or contained one in the other. Here, a parametrized weakening of this condition is introduced. Let us say that a set system $\mathcal{F} \subseteq 2^X$ is $t$-laminar if $A,B \in \mathcal{F}$ with $|A \cap B| \ge t$ implies $A \subseteq B$ or $B \subseteq A$. We obtain very close asymptotic bounds in terms of $n$ on the maximum size of a $2$-laminar family $\mathcal{F} \subseteq 2^{[n]}$. A construction for $3$-laminar families and a crude analysis for general $t$ are also given.
- Publication:
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arXiv e-prints
- Pub Date:
- June 2014
- DOI:
- arXiv:
- arXiv:1406.3077
- Bibcode:
- 2014arXiv1406.3077D
- Keywords:
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- Mathematics - Combinatorics