Relationships between NP-sets, Co-NP-sets, and P-sets relative to random oracles

Abstract

It is proved that relative to random oracle A (with respect to the uniform measure) the following assertions hold: (1) there is a pair of disjoint NP/sup A/-sets that are separable by no P/sup A/-set, (2) there is a pair of disjoint Co-NP/sup A/-sets that are separable by no P/sup A/-set, and (3) there is an infinite Co-NP/sup A/-set having no infinite NP/sup A/-subset.<>