Competing Provers Yield Improved Karp-Lipton Collapse Results

  • Authors:
  • Jin-yi Cai;Venkatesan T. Chakaravarthy;Lane A. Hemaspaandra;Mitsunori Ogihara

  • Affiliations:
  • -;-;-;-

  • Venue:
  • STACS '03 Proceedings of the 20th Annual Symposium on Theoretical Aspects of Computer Science
  • Year:
  • 2003

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Abstract

Via competing provers, we show that if a language A is self-reducible and has polynomial-size circuits then S2A = S2. Building on this, we strengthen the K盲mper-AFK Theorem, namely, we prove that if NP 驴 (NP 驴 coNP)/poly then the polynomial hierarchy collapses to S2NP驴coNP. We also strengthen Yap's Theorem, namely, we prove that if NP 驴 coNP/poly then the polynomial hierarchy collapses to S2NP. Under the same assumptions, the best previously known collapses were to ZPPNP and ZPPNPNP respectively ([20,6], building on [18,1,17,30]). It is known that S2 驴 ZPPNP [8]. That result and its relativized version show that our new collapses indeed improve the previously known results. Since the K盲mper-AFK Theorem and Yap's Theorem are used in the literature as bridges in a variety of results--ranging from the study of unique solutions to issues of approximation--our results implicitly strengthen all those results.