Two situations with unit-cost: ordered abelian semi-groups and some commutative rings

  • Authors:
  • Mihai Prunescu

  • Affiliations:
  • Universität Freiburg, Germany and I.M.A.R., Bucharest, Romania

  • Venue:
  • Journal of Complexity - Festschrift for the 70th birthday of Arnold Schönhage
  • Year:
  • 2005

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Abstract

The paper presents two situations where unit-cost complexity results are closely related with results from the classical computability. * In Section 2 we study an important theorem by Koiran and Fournier from an axiomatic point of view. It is proved that the algebraic Knapsack problem belongs to P over some ordered abelian semi-group iff P=NP classically. In this case there would exist a unit-cost machine solving the algebraic Knapsack problem over all ordered abelian semi-groups in some uniform polynomial time. * In Section 3 we apply the theorem of Matiyasevich in order to construct a ring with PNBPNP and such that its polynomial hierarchy does not collapse at any level.