The Kolmogorov-Loveland Stochastic Sequences Are Not Closed under Selecting Subsequences

  • Authors:
  • Wolfgang Merkle

  • Affiliations:
  • -

  • Venue:
  • ICALP '02 Proceedings of the 29th International Colloquium on Automata, Languages and Programming
  • Year:
  • 2002

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Abstract

It is shown that the class of Kolmogorov-Loveland stochastic sequences is not closed under selecting subsequences by monotonic computable selection rules. This result gives a strong negative answer to the question whether the Kolmogorov-Loveland stochastic sequences are closed under selecting subsequences by Kolmogorov-Loveland selection rules, i.e., by not necessarily monotonic, partially computable selection rules. The following previously known results are obtained as corollaries. The Mises-Wald-Church stochastic sequences are not closed under computable permutations, hence in particular they form a strict superclass of the class of Kolmogorov-Loveland stochastic sequences. The Kolmogorov-Loveland selection rules are not closed under composition.