Separating the notions of self- and autoreducibility

  • Authors:
  • Piotr Faliszewski;Mitsunori Ogihara

  • Affiliations:
  • Department of Computer Science, University of Rochester, Rochester;Department of Computer Science, University of Rochester, Rochester

  • Venue:
  • MFCS'05 Proceedings of the 30th international conference on Mathematical Foundations of Computer Science
  • Year:
  • 2005

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Abstract

Recently Glaßer et al. have shown that for many classes C including PSPACE and NP it holds that all of its nontrivial many-one complete languages are autoreducible. This immediately raises the question of whether all many-one complete languages are Turing self-reducible for such classes C. This paper considers a simpler version of this question—whether all PSPACE-complete (NP-complete) languages are length-decreasing self-reducible. We show that if all PSPACE-complete languages are length-decreasing self-reducible then PSPACE = P and that if all NP-complete languages are length-decreasing self-reducible then NP = P. The same type of result holds for many other natural complexity classes. In particular, we show that (1) not all NL-complete sets are logspace length-decreasing self-reducible, (2) unconditionally not all PSPACE-complete languages are logpsace length-decreasing self-reducible, and (3) unconditionally not all PSPACE-complete languages are polynomial-time length-decreasing self-reducible.