Optimal simulations between unary automata

  • Carlo Mereghetti
  • Giovanni Pighizzini
Automata and Formal Languages I
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1373)


We consider the problem of computing the costs — in terms of states — of optimal simulations between different kinds of finite automata recognizing unary languages. Our main result is a tight simulation of unary n-state two-way nondeterministic automata by \(O(e^{\sqrt {n \ln n} } )\)-state one-way deterministic automata. In addition, we show that, given a unary n-state two-way nondeterministic automaton, one can construct an equivalent O(n 2)-state two-way nondeterministic automaton performing both input head reversals and nondeterministic choices at the endmarkers only. Further results on simulating unary alternating finite automata are pointed out. Our results give answers to some questions left open in the literature.


Finite Automaton Elementary Circuit Great Common Divisor Computation Path Optimal Simulation 


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Copyright information

© Springer-Verlag 1998

Authors and Affiliations

  • Carlo Mereghetti
    • 1
  • Giovanni Pighizzini
    • 1
  1. 1.Dipartimento di Scienze dell'InformazioneUniversità degli Studi di MilanoMilanoItaly

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