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International Conference on Developments in Language Theory

DLT 2010: Developments in Language Theory pp 197–208Cite as

Two-Way Unary Automata versus Logarithmic Space

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Part of the book series: Lecture Notes in Computer Science ((LNTCS,volume 6224))

Abstract

We show that each n-state unary 2nfa (a two-way nondeterministic finite automaton) can be simulated by an equivalent 2ufa (an unambiguous 2nfa) with a polynomial number of states. Moreover, if L = NL (the classical logarithmic space classes), then each unary 2nfa can be converted into an equivalent 2dfa (a deterministic two-way automaton), still keeping polynomial the number of states. This shows a connection between the standard logarithmic space complexity and the state complexity of two-way unary automata: it indicates that L could be separated from NL by proving a superpolynomial gap, in the number of states, for the conversion from unary 2NFAs to 2DFAs.

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Author information

Authors and Affiliations

  1. Department of Computer Science, P. J. Šafárik University, Jesenná 5, SK-04001, Košice, Slovakia

    Viliam Geffert

  2. Dipartimento di Informatica e Comunicazione, Università degli Studi di Milano, via Comelico 39, I-20135, Milano, Italy

    Giovanni Pighizzini

Authors
  1. Viliam Geffert
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  2. Giovanni Pighizzini
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Editor information

Editors and Affiliations

  1. Dept. of Computer Science, University of Western Ontario, N6A 5B7, London, ON, Canada

    Yuan Gao , Hanlin Lu , Shinnosuke Seki  & Sheng Yu , ,  & 

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Geffert, V., Pighizzini, G. (2010). Two-Way Unary Automata versus Logarithmic Space. In: Gao, Y., Lu, H., Seki, S., Yu, S. (eds) Developments in Language Theory. DLT 2010. Lecture Notes in Computer Science, vol 6224. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-14455-4_19

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  • DOI: https://doi.org/10.1007/978-3-642-14455-4_19

  • Publisher Name: Springer, Berlin, Heidelberg

  • Print ISBN: 978-3-642-14454-7

  • Online ISBN: 978-3-642-14455-4

  • eBook Packages: Computer ScienceComputer Science (R0)

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