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2 votes
1 answer
131 views

Turán density of hypergraphs with very few edges

As usual, for an $r$-uniform hypergraph $G$, denote by $ex_r(n,G)$ the maximum number of edges an $r$-uniform, $G$-free hypergraph on $n$ vertices can have, and let $\lim \frac{ex_r(n,G)}{\binom nr}\...
domotorp's user avatar
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4 votes
1 answer
137 views

On the number of disjoint subsets of a large set families

Let $[n] := \{1,\dots,n\}$, for some large integer $n$, and let $\mathcal{F}$ be a family of 2-element subsets of $[n]$. The famous Erdös-Ko-Rado (EKR) theorem says that if $|\mathcal{F}| > {n - 1 ...
John Hans's user avatar
1 vote
0 answers
79 views

Partitioning of a set family that avoids small intersections

Let $\mathcal{F}$ be the family of all $k$-element subsets of $[n]$. What is the smallest $\ell$ such that we can partition $\mathcal{F}$ into $\ell$ families $F_1,\dots,F_\ell$ with the property that ...
wandering_lambda's user avatar
4 votes
1 answer
220 views

Maximal number of perfect matchings that pairwise form a Hamiltonian cycle

Definition: Let $MH(n)$ be the maximal number of perfect matchings (1-regular graphs) on $n$ vertices where the union of any two perfect matchings is a Hamiltonian cycle. Question: Is it true that $MH(...
Daniel Soltész's user avatar