Geometrical realization of set systems and probabilistic communication complexity

  • Authors:
  • N. Alon;P. Frankl;V. Rodl

  • Affiliations:
  • -;-;-

  • Venue:
  • SFCS '85 Proceedings of the 26th Annual Symposium on Foundations of Computer Science
  • Year:
  • 1985

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Abstract

Let d = d(n) be the minimum d such that for every sequence of n subsets F1, F2, . . . , Fn of {1, 2, . . . , n} there exist n points P1, P2, . . . , Pn and n hyperplanes H1, H2 .... , Hn in Rd such that Pj lies in the positive side of Hi iff j ∈ Fi. Then n/32 ≤ d(n) ≤ (1/2 + 0(1)) ċ n. This implies that the probabilistic unbounded-error 2-way complexity of almost all the Boolean functions of 2p variables is between p-5 and p, thus solving a problem of Yao and another problem of Paturi and Simon. The proof of (1) combines some known geometric facts with certain probabilistic arguments and a theorem of Milnor from real algebraic geometry.