A note on alternating one-pebble Turing machines with sublogarithmic space

  • Authors:

  • Andrzej Szepietowski

  • Affiliations:

  • Institute of Mathematics, University of Gdańsk, ul. Wita Stwosza, Gdańsk, Poland

  • Venue:
  • Information Processing Letters
  • Year:
  • 2006

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Abstract

Inoue et al. [A. Inoue, A. Ito, K. Inoue, T. Okazaki, Some properties of one-pebble Turing machines with sublogarithmic space, Theoret. Comput. Sci. 341 (2005) 138-149] conjectured that the language {ww | w ∈ {a, b}+} is not accepted by any alternating one-pebble Turing machine with sublogarithmic space. In this paper we disprove the conjecture by showing that there exists an alternating one-pebble Turing machine accepting the language in log log n space.