
doi: 10.1002/rsa.20267
AbstractWe give a very short proof of an Erdős conjecture that the number of edges in a non‐2‐colorable n‐uniform hypergraph is at least f(n)2n, where f(n) goes to infinity. Originally it was solved by József Beck in 1977, showing that f(n) at least clog n. With an ingenious recoloring idea he later proved that f(n) ≥ cn1/3+o(1). Here we prove a weaker bound on f(n), namely f(n) ≥ cn1/4. Instead of recoloring a random coloring, we take the ground set in random order and use a greedy algorithm to color. The same technique works for getting bounds on k‐colorability. It is also possible to combine this idea with the Lovász Local Lemma, reproving some known results for sparse hypergraphs (e.g., the n‐uniform, n‐regular hypergraphs are 2‐colorable if n ≥ 8). © 2009 Wiley Periodicals, Inc. Random Struct. Alg., 2009
greedy algorithm, Coloring of graphs and hypergraphs, regular, Hypergraphs, coloring hypergraph
greedy algorithm, Coloring of graphs and hypergraphs, regular, Hypergraphs, coloring hypergraph
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