Reversible Multi-head Finite Automata Characterize Reversible Logarithmic Space

  • Holger Bock Axelsen
Part of the Lecture Notes in Computer Science book series (LNCS, volume 7183)


Deterministic and non-deterministic multi-head finite automata are known to characterize the deterministic and non- deterministic logarithmic space complexity classes, respectively. Recently, Morita introduced reversible multi-head finite automata (RMFAs), and posed the question of whether RMFAs characterize reversible logarithmic space as well. Here, we resolve the question affirmatively, by exhibiting a clean RMFA simulation of logarithmic space reversible Turing machines. Indirectly, this also proves that reversible and deterministic multi-head finite automata recognize the same languages.


Turing Machine Transition Rule Unary Counter Input Tape Track Head 
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© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Holger Bock Axelsen
    • 1
  1. 1.DIKU, Department of Computer ScienceUniversity of CopenhagenDenmark

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