Bernd Borchert, Dietrich Kuske, Frank Stephan

Pin & Weil [PW95] characterized the automata of existentially

first-order definable languages. We will use this result for the following

characterization of the complexity class NP. Assume that the

Polynomial-Time Hierarchy does not collapse. Then a regular language

L characterizes NP as an unbalanced polynomial-time leaf language

if and ...
more >>>