Lower bounds for circuits with few modular and symmetric gates

  • Authors:
  • Arkadev Chattopadhyay;Kristoffer Arnsfelt Hansen

  • Affiliations:
  • School of Computer Science, McGill University;Department of Computer Science, University of Aarhus, Denmark

  • Venue:
  • ICALP'05 Proceedings of the 32nd international conference on Automata, Languages and Programming
  • Year:
  • 2005

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Abstract

We consider constant depth circuits augmented with few modular, or more generally, arbitrary symmetric gates. We prove that circuits augmented with o(log2n) symmetric gates must have size n$^{\Omega({\rm log}\ {\it n})}$ to compute a certain (complicated) function in ACC0. This function is also hard on the average for circuits of size n$^{\epsilon log {\it n}}$ augmented with o(log n) symmetric gates, and as a consequence we can get a pseudorandom generator for circuits of size m containing $o(\sqrt{{\rm log} \ m})$ symmetric gates. For a composite integer m having r distinct prime factors, we prove that circuits augmented with sMODm gates must have size ${\it n}^{\Omega(\frac{1}{s}{\rm log}^{\frac{1}{r-1}}n)}$ to compute MAJORITY or MODl, if l has a prime factor not dividing m. For proving the latter result we introduce a new notion of representation of boolean function by polynomials, for which we obtain degree lower bounds that are of independent interest.