Structural properties of nondeterministic complete sets

Two aspects of the structure of complete sets for NE and larger nondeterministic time classes are surveyed. First, differences between complete sets arising from various polynomial-time reductions are proved. Immunity properties of these complete sets are then considered. It is shown that NE-complete sets (and their complements) have dense E subsets and dense UP subsets. All of these results hold for nondeterministic time classes containing NE. Some consequences for NP are noted.<<ETX>>

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