
arXiv: 1002.0149
AbstractLet $\alpha_1,\ldots,\alpha_k$ satisfy $\sum_i\alpha_i=1$ and suppose a k‐uniform hypergraph on n vertices satisfies the following property; in any partition of its vertices into k sets $A_1,\ldots,A_k$ of sizes $\alpha_1n,\ldots,\alpha_kn$, the number of edges intersecting $A_1,\ldots,A_k$ is (asymptotically) the number one would expect to find in a random k‐uniform hypergraph. Can we then infer that H is quasi‐random? We show that the answer is negative if and only if $\alpha_1=\cdots=\alpha_k=1/k$. This resolves an open problem raised in 1991 by Chung and Graham [J AMS 4 (1991), 151–196].While hypergraphs satisfying the property corresponding to $\alpha_1=\cdots=\alpha_k=1/k$ are not necessarily quasi‐random, we manage to find a characterization of the hypergraphs satisfying this property. Somewhat surprisingly, it turns out that (essentially) there is a unique non quasi‐random hypergraph satisfying this property. The proofs combine probabilistic and algebraic arguments with results from the theory of association schemes. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2011
cut properties, Random graphs (graph-theoretic aspects), hypergraph, FOS: Mathematics, Association schemes, strongly regular graphs, Mathematics - Combinatorics, Combinatorics (math.CO), quasi-randomness, Hypergraphs
cut properties, Random graphs (graph-theoretic aspects), hypergraph, FOS: Mathematics, Association schemes, strongly regular graphs, Mathematics - Combinatorics, Combinatorics (math.CO), quasi-randomness, Hypergraphs
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