Redundancy of minimal weight expansions in Pisot bases

  • Authors:
  • Peter J. Grabner;Wolfgang Steiner

  • Affiliations:
  • Institut für Analysis und Computational Number Theory, Technische Universität Graz, Steyrergasse 30, 8010 Graz, Austria;LIAFA, CNRS, Université Paris DiderotParis 7, Case 7014, 75205 Paris Cedex 13, France

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2011

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Abstract

Motivated by multiplication algorithms based on redundant number representations, we study representations of an integer n as a sum n=@?"k@e"kU"k, where the digits @e"k are taken from a finite alphabet @S and (U"k)"k is a linear recurrent sequence of Pisot type with U"0=1. The most prominent example of a base sequence (U"k)"k is the sequence of Fibonacci numbers. We prove that the representations of minimal weight @?"k|@e"k| are recognised by a finite automaton and obtain an asymptotic formula for the average number of representations of minimal weight. Furthermore, we relate the maximal number of representations of a given integer to the joint spectral radius of a certain set of matrices.