Fixed-Polynomial Size Circuit Bounds Lance Fortnow Rahul Santhanam Ryan Williams Northwestern University University of Edinburgh Institute for Advanced Study Evanston, IL, USA Edinburgh, Scotland, UK Princeton, NJ, USA
[email protected] [email protected] [email protected] P Abstract—In 1982, Kannan showed that Σ2 does not have this question remains open for NP – we do not even know k n -sized circuits for any k. Do smaller classes also admit of superlinear size lower bounds for NP. such circuit lower bounds? Despite several improvements of Kannan’s result, we still cannot prove that PNP does not have However, we do have such lower bounds for some classes linear size circuits. Work of Aaronson and Wigderson provides slightly above NP. In 1982, Kannan [Kan82] proved that strong evidence – the “algebrization” barrier – that current P k Σ2 does not have n -sized circuits for any k. This re- techniques have inherent limitations in this respect. sult was progressively improved using relativizing tech- We explore questions about fixed-polynomial size circuit niques ([BCG+96], [KW98], [Cai07]) culminating in the lower bounds around and beyond the algebrization barrier. analogous circuit lower bound for SP [Cai07]. We find several connections, including 2 Recently, non-relativizing techniques from the theory of • The following are equivalent: k k interactive proofs have been applied to this problem. In 2005, – NP is in SIZE(n ) (has O(n )-size circuit families) Vinodchandran [Vin05] showed that the class PP does not for some k nc k k – For each c, PNP[ ] is in SIZE(n ) for some k have n -sized circuits.