On lower bounds for constant width arithmetic circuits

Abstract

For every k>1, we give an explicit polynomial that is computable by a linear-sized monotone circuit of width 2k but has no subexponential-sized monotone circuit of width k. As a consequence we show that the constant-width and the constant-depth hierarchies of monotone arithmetic circuits (both commutative and noncommutative) are infinite. We also prove hardness-randomness tradeoffs for identity testing of constant-width circuits analogous to [6,4]. © 2009 Springer-Verlag Berlin Heidelberg.