Randomly supported independence and resistance

  • Authors:
  • Per Austrin;Johan Håstad

  • Affiliations:
  • KTH - Royal Institute of Technology, Stockholm, Sweden;KTH - Royal Institute of Technology, Stockholm, Sweden

  • Venue:
  • Proceedings of the forty-first annual ACM symposium on Theory of computing
  • Year:
  • 2009

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Abstract

We prove that for any positive integer k, there is a constant ck such that a randomly selected set of ck nk log n Boolean vectors with high probability supports a balanced k-wise independent distribution. In the case of k ≤ 2 a more elaborate argument gives the stronger bound ck nk. Using a recent result by Austrin and Mossel this shows that a predicate on t bits, chosen at random among predicates accepting c2 t2 input vectors, is, assuming the Unique Games Conjecture, likely to be approximation resistant. These results are close to tight: we show that there are other constants, ck', such that a randomly selected set of cardinality ck' nk points is unlikely to support a balanced k-wise independent distribution and, for some c0, a random predicate accepting ct2/log t input vectors is non-trivially approximable with high probability. In a different application of the result of Austrin and Mossel we prove that, again assuming the Unique Games Conjecture, any predicate on t bits accepting at least (32/33) • 2t inputs is approximation resistant. The results extend from the Boolean domain to larger finite domains.