Non-approximability of the randomness deficiency function

  • Authors:
  • Michael A. Ustinov

  • Affiliations:
  • Moscow State University

  • Venue:
  • CSR'06 Proceedings of the First international computer science conference on Theory and Applications
  • Year:
  • 2006

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Abstract

Let x be a binary string of length n. Consider the set Px of all pairs of integers (a,b) such that the randomness deficiency of x in a finite set S of Kolmogorov complexity at most a is at most b. The paper [4] proves that there is no algorithm that for every given x upper semicomputes the minimal deficiency function βx(a)=min{b | (a,b)∈px}with precision n/log4n. We strengthen this result in two respects. First, we improve the precision to n/4. Second, we show that there is no algorithm that for every given x enumerates a set at distance at most n/4 from Px, which is easier than to upper semicompute the minimal deficiency function of x with the same accuracy.