slideshow 3

Logic seminar

Consistency of circuit evaluation, extended resolution and total NP search problems

Jan Krajíček
MFF UK

 

Monday, 26. October 2015 - 13:30 to 15:00

in IM, rear building, ground floor

We consider sets Γ(n,s,k) of narrow clauses expressing that no definition of a size s circuit with n inputs is refutable in resolution R in k steps. We show that every CNF shortly refutable in Extended R, ER, can be easily reduced to an instance of Γ(0,s,k) (with s,k depending on the size of the ER-refutation) and, in particular, that Γ(0,s,k) when interpreted as a relativized NP search problem is complete among all such problems provably total in the bounded arithmetic theory V^1_1. We use the ideas of implicit proofs to define from Γ(0,s,k) a non-relativized NP search problem iΓ and we show that it is complete among all such problems provably total in bounded arithmetic theory V^1_2. The reductions are definable in S12. We indicate how similar results can be proved for some other propositional proof systems and bounded arithmetic theories and how the construction can be used to define specific random unsatisfiable formulas, and we formulate two open problems about them.