A Turan Problem for Cartesian Products of Hypergraphs

D. de Caen1, D. L. Kreher2, J. A. Wiseman3
1Department of Mathematics Queens University Kingston, Ontario K7L 3N6 CANADA
2Department of Mathematics University of Wyoming Laramie, Wyoming 82071 ULS.A.
3Department of Mathematics Rochester Institute of Technology Rochester, New York 14623 ULS.A.

Abstract

Let \(S\) and \(T\) be sets with \(|S| = m\) and \(|T| = n\). Let \(S_3, S_2\) and \(T_3, T_2\) be the sets of all \(3\)-subsets (\(2\)-subsets) of \(S\) and \(T\), respectively. Define \(Q((m, 2, 3), (n, 2, 3))\) as the smallest subset of \(S_2 \times T_2\) needed to cover all elements of \(S_3 \times T_3\). A more general version of this problem is initially defined, but the bulk of the investigation is devoted to studying this number. Its property as a lower bound for a planar crossing number is the reason for this focus.