123 research outputs found

    A note on tilted Sperner families with patterns

    Get PDF
    Let pp and qq be two nonnegative integers with p+q>0p+q>0 and n>0n>0. We call FP([n])\mathcal{F} \subset \mathcal{P}([n]) a \textit{(p,q)-tilted Sperner family with patterns on [n]} if there are no distinct F,GFF,G \in \mathcal{F} with: (i)  pFG=qGF, and(i) \ \ p|F \setminus G|=q|G \setminus F|, \ \textrm{and} (ii) f>g for all fFG and gGF.(ii) \ f > g \ \textrm{for all} \ f \in F \setminus G \ \textrm{and} \ g \in G \setminus F. Long (\cite{L}) proved that the cardinality of a (1,2)-tilted Sperner family with patterns on [n][n] is O(e120logn 2nn).O(e^{120\sqrt{\log n}}\ \frac{2^n}{\sqrt{n}}). We improve and generalize this result, and prove that the cardinality of every (p,qp,q)-tilted Sperner family with patterns on [nn] is O(logn 2nn).O(\sqrt{\log n} \ \frac{2^n}{\sqrt{n}}).Comment: 8 page

    On Tur\'an problems with bounded matching number

    Full text link
    Very recently, Alon and Frankl initiated the study of the maximum number of edges in nn-vertex FF-free graphs with matching number at most ss. For fixed FF and ss, we determine this number apart from a constant additive term. We also obtain several exact results

    Rainbow copies of FF in families of HH

    Full text link
    We study the following problem. How many distinct copies of HH can an nn-vertex graph GG have, if GG does not contain a rainbow FF, that is, a copy of FF where each edge is contained in a different copy of HH? The case H=KrH=K_r is equivalent to the Tur\'an problem for Berge hypergraphs, which has attracted several researchers recently. We also explore the connection of our problem to the so-called generalized Tur\'an problems. We obtain several exact results. In the particularly interesting symmetric case where H=FH=F, we completely solve the case FF is the 3-edge path, and asymptitically solve the case FF is a book graph
    corecore