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Logical reducibility and monadic NP

By: Cosmadakis, S.S.;

1993 / IEEE / 0-8186-4370-6


This item was taken from the IEEE Periodical ' Logical reducibility and monadic NP ' It is shown that, by choosing appropriate encodings of instances as relational structures, several known polynomial-time many-one reductions can he described in first-order logic, and furthermore they are monadic. As a corollary, several known NP-complete problems in monadic NP are shown not to be in monadic co-NP. It is further shown that there is no monadic first-order reduction from connectivity to directed reachability, even in the presence of successor. Finally, some classes of syntactically restricted first-order reductions are shown to be incomparable.<>