Dimensions of copeland-erdös sequences

  • Authors:
  • Xiaoyang Gu;Jack H. Lutz;Philippe Moser

  • Affiliations:
  • Department of Computer Science, Iowa State University, Ames, IA;Department of Computer Science, Iowa State University, Ames, IA;Department of Computer Science, Iowa State University, Ames, IA

  • Venue:
  • FSTTCS '05 Proceedings of the 25th international conference on Foundations of Software Technology and Theoretical Computer Science
  • Year:
  • 2005

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Abstract

The base-kCopeland-Erdös sequence given by an infinite set A of positive integers is the infinite sequence CEk(A) formed by concatenating the base-k representations of the elements of A in numerical order. This paper concerns the following four quantities.The finite-state dimension dimFS (CEk(A)), a finite-state version of classical Hausdorff dimension introduced in 2001. The finite-state strong dimension DimFS(CEk(A)), a finite-state version of classical packing dimension introduced in 2004. This is a dual of dimFS(CEk(A)) satisfying DimFS(CEk(A)) ≥dimFS(CEk(A)). The zeta-dimension Dimζ(A), a kind of discrete fractal dimension discovered many times over the past few decades. The lower zeta-dimension dimζ(A), a dual of Dimζ(A) satisfying dimζ(A)≤Dimζ(A). We prove the following. dimFS(CEk(A)) ≥dimζ(A). This extends the 1946 proof by Copeland and Erdös that the sequence CEk(PRIMES) is Borel normal. DimFS(CEk(A))≥Dimζ(A). These bounds are tight in the strong sense that these four quantities can have (simultaneously) any four values in [0,1] satisfying the four above-mentioned inequalities.