On complexity of regular realizability problems

Abstract

A regular realizability (RR) problem is testing nonemptiness of intersection of some fixed language (filter) with given regular language. We study here complexity of RR problems. It appears that for any language L there exists RR problem equivalent to L under disjunctive reductions on nondeterministic log space. It implies that for any level of polynomial hierarchy there exists complete RR problem under polynomial reductions.

Submitted to Problems of Information Transmission. Corrected and extended version, main results are the same