One Alternation Can Be More Powerful Than Randomization in Small and Fast Two-Way Finite Automata

  • Kaspars Balodis
Part of the Lecture Notes in Computer Science book series (LNCS, volume 8070)


We show a family of languages that can be recognized by a family of linear-size alternating one-way finite automata with one alternation but cannot be recognized by any family of polynomial-size bounded-error two-way probabilistic finite automata with the expected runtime bounded by a polynomial. In terms of finite automata complexity theory this means that neither 1Σ2 nor 1Π2 is contained in 2P 2.


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© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Kaspars Balodis
    • 1
  1. 1.Faculty of ComputingUniversity of LatviaRigaLatvia

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