On the computational power of PP and (+)P

  • Authors:
  • S. Toda

  • Affiliations:
  • Dept. of Comput. Sci.&Inf. Math., Univ. of Electro-Commun., Tokyo, Japan

  • Venue:
  • SFCS '89 Proceedings of the 30th Annual Symposium on Foundations of Computer Science
  • Year:
  • 1989

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Abstract

Two complexity classes, PP and (+)P, are compared with PH (the polynomial-time hierarchy). The main results are as follows: (1) every set in PH is reducible in a certain sense to a set in PP, an (2) every set in PH is reducible to a set in (+)P under randomized polynomial-time reducibility with two-sided bounded error probability. It follows from these results that neither PP nor (+)P is a subset of or equivalent to PH unless PH collapses to a finite level. This is strong evidence that both classes are strictly harder than PH.