Speeding-up single-tape nondeterministic computations by single alternation, with separation results

  • Jiří Wiedermann
Session 8: Complexity Theory
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1099)


It is shown that for any well behaved function T(n), any single-tape nondeterministic Turing Machine of time complexity T(n) can be simulated by a single-tape Σ2-machine in time T(n)/logT(n). A similar result holds also for complementary, single-tape co-nondeter-ministic and II2machines. Consequently, NTIME1(T(n)) is strictly contained in Σ2-TIME1(T(n)), and analogously co-TIME1(T(n)) in II2-TIME1(T(n)), i.e., for single tape nondeterministic or co-nondeterministic machines adding of one more alternation leads to provably more powerful machines.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1996

Authors and Affiliations

  • Jiří Wiedermann
    • 1
  1. 1.Institute of Computer ScienceAcademy of Sciences of the Czech RepublicPragueCzech Republic

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