On Oscillation-free ε-random Sequences

  • Authors:
  • Ludwig Staiger

  • Affiliations:
  • Institut für Informatik, Martin-Luther-Universität Halle-Wittenberg, D--06099 Halle, Germany

  • Venue:
  • Electronic Notes in Theoretical Computer Science (ENTCS)
  • Year:
  • 2008

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Abstract

In this paper we discuss three notions of partial randomness or @e-randomness. @e-randomness should display all features of randomness in a scaled down manner. However, as Reimann and Stephan [J. Reimann, and F. Stephan, On hierarchies of randomness tests, in: Mathematical Logic in Asia, Proceedings of the 9th Asian Logic Conference, Novosibirsk, World Scientific, Singapore 2006] proved, Tadaki [K. Tadaki, A generalization of Chaitin's halting probability @Wand halting self-similar sets, Hokkaido Math. J. 31 (2002), 219-253] and Calude et al. [C.S. Calude, L. Staiger, and S.A. Terwijn. On partial randomness, Annals of Applied and Pure Logic, 138 (2006), 20-30] proposed at least three different concepts of partial randomness. We show that all of them satisfy the natural requirement that any @e-non-null set contains an @e-random infinite word. This allows us to focus our investigations on the strongest one which is based on a priori complexity. We investigate this concept of partial randomness and show that it allows-similar to the random infinite words-oscillation-free (w.r.t. to a priori complexity) @e-random infinite words if only @e is a computable number. The proof uses the dilution principle. Alternatively, for certain sets of infinite words (@w-languages) we show that their most complex infinite words are oscillation-free @e-random. Here the parameter @e is also computable and depends on the set chosen.