A Katona-type proof of an Erdős-Ko-Rado-type theorem

  • Authors:
  • Ehud Friedgut

  • Affiliations:
  • Institute of Mathematics, Hebrew University, Jerusalem, Israel

  • Venue:
  • Journal of Combinatorial Theory Series A
  • Year:
  • 2005

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Abstract

Let p ≤ 1/2 and let µp be the product measure on {0, 1}n, where µp(x) = pΣxi(1 - p)n-Σxi. Let A ⊂ {0, 1}n be an intersecting family, i.e. for every x, y ∈ A there exists 1 ≤ i ≤ n such that xi = Yi = 1. Then µp(A) ≤ p. Our proof uses a probabilistic trick first applied by Katona to prove the Erdös-Ko-Rado theorem.