Forbidding Complete Hypergraphs as Traces

被引:0
|
作者
Dhruv Mubayi
Yi Zhao
机构
[1] University of Illinois,Department of Mathematics, Statistics, and Computer Science
[2] Georgia State University,Department of Mathematics and Statistics
来源
Graphs and Combinatorics | 2007年 / 23卷
关键词
Trace; hypergraph; turán problem; extremal problem;
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学科分类号
摘要
Let 2 ≤q ≤min{p, t − 1} be fixed and n → ∞. Suppose that \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal{F}$$\end{document} is a p-uniform hypergraph on n vertices that contains no complete q-uniform hypergraph on t vertices as a trace. We determine the asymptotic maximum size of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathcal{F}}$$\end{document} in many cases. For example, when q = 2 and p∈{t, t + 1}, the maximum is \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$( \frac{n}{t-1})^{t-1} + o(n^{t-1})$$\end{document} , and when p = t = 3, it is \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lfloor \frac{(n-1)^2}{4}\rfloor$$\end{document} for all n≥ 3. Our proofs use the Kruskal-Katona theorem, an extension of the sunflower lemma due to Füredi, and recent results on hypergraph Turán numbers.
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页码:667 / 679
页数:12
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