A new rank technique for formula size lower bounds

  • Authors:
  • Troy Lee

  • Affiliations:
  • LRI, Université Paris-Sud

  • Venue:
  • STACS'07 Proceedings of the 24th annual conference on Theoretical aspects of computer science
  • Year:
  • 2007

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Abstract

We introduce a new technique for proving formula size lower bounds based on matrix rank. A simple form of this technique gives bounds at least as large as those given by the method of Khrapchenko, originally used to prove an n2 lower bound on the parity function. Applying our method to the parity function, we are able to give an exact expression for the formula size of parity: if n = 2l + k, where 0 ≤ k l, then the formula size of parity on n bits is exactly 2l(2l+3k) = n2+k2l-k2. Such a bound cannot be proven by any of the lower bound techniques of Khrapchenko, Nečiporuk, Koutsoupias, or the quantum adversary method, which are limited by n2.