748 research outputs found
Minimal weight expansions in Pisot bases
For applications to cryptography, it is important to represent numbers with a
small number of non-zero digits (Hamming weight) or with small absolute sum of
digits. The problem of finding representations with minimal weight has been
solved for integer bases, e.g. by the non-adjacent form in base~2. In this
paper, we consider numeration systems with respect to real bases which
are Pisot numbers and prove that the expansions with minimal absolute sum of
digits are recognizable by finite automata. When is the Golden Ratio,
the Tribonacci number or the smallest Pisot number, we determine expansions
with minimal number of digits and give explicitely the finite automata
recognizing all these expansions. The average weight is lower than for the
non-adjacent form
Beta-expansions, natural extensions and multiple tilings associated with Pisot units
From the works of Rauzy and Thurston, we know how to construct (multiple)
tilings of some Euclidean space using the conjugates of a Pisot unit
and the greedy -transformation. In this paper, we consider different
transformations generating expansions in base , including cases where
the associated subshift is not sofic. Under certain mild conditions, we show
that they give multiple tilings. We also give a necessary and sufficient
condition for the tiling property, generalizing the weak finiteness property
(W) for greedy -expansions. Remarkably, the symmetric
-transformation does not satisfy this condition when is the
smallest Pisot number or the Tribonacci number. This means that the Pisot
conjecture on tilings cannot be extended to the symmetric
-transformation. Closely related to these (multiple) tilings are natural
extensions of the transformations, which have many nice properties: they are
invariant under the Lebesgue measure; under certain conditions, they provide
Markov partitions of the torus; they characterize the numbers with purely
periodic expansion, and they allow determining any digit in an expansion
without knowing the other digits
Redundancy of minimal weight expansions in Pisot bases
Motivated by multiplication algorithms based on redundant number
representations, we study representations of an integer as a sum , where the digits are taken from a finite alphabet
and is a linear recurrent sequence of Pisot type with
. The most prominent example of a base sequence is the
sequence of Fibonacci numbers. We prove that the representations of minimal
weight 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 order of magnitude of the number of
representations of a given integer to the joint spectral radius of a certain
set of matrices
Rational self-affine tiles
An integral self-affine tile is the solution of a set equation , where
is an integer matrix and is a finite
subset of . In the recent decades, these objects and the induced
tilings have been studied systematically. We extend this theory to matrices
. We define rational self-affine tiles
as compact subsets of the open subring of the ad\'ele ring , where the factors of the
(finite) product are certain -adic completions of a number field
that is defined in terms of the characteristic polynomial of .
Employing methods from classical algebraic number theory, Fourier analysis in
number fields, and results on zero sets of transfer operators, we establish a
general tiling theorem for these tiles. We also associate a second kind of
tiles with a rational matrix. These tiles are defined as the intersection of a
(translation of a) rational self-affine tile with . Although these intersection
tiles have a complicated structure and are no longer self-affine, we are able
to prove a tiling theorem for these tiles as well. For particular choices of
digit sets, intersection tiles are instances of tiles defined in terms of shift
radix systems and canonical number systems. Therefore, we gain new results for
tilings associated with numeration systems
Wages in the East German transition process: facts and explanations
We analyze wage developments in the East German transition process both at the macro and at the microeconomic level. At the macroeconomic level, we draw special attention to the important distinction between product and consumption wages, describe the development of various wage measures, labor productivity and unit labor costs in East Germany in relation to West Germany, and relate these developments to the system of collective wage bargaining. At the microeconomic level, we describe changes in the distribution of hourly wages between 1990 and 1997 and analyze the economic factors determining these changes by way of empirical wage functions estimated on the basis of the Socio? Economic Panel for East Germany. The paper also draws some conclusions on the likely future course of the East-West German wage convergence process. --
Metrical theory for -Rosen fractions
The Rosen fractions form an infinite family which generalizes the
nearest-integer continued fractions. In this paper we introduce a new class of
continued fractions related to the Rosen fractions, the -Rosen
fractions. The metrical properties of these -Rosen fractions are
studied. We find planar natural extensions for the associated interval maps,
and show that these regions are closely related to similar region for the
'classical' Rosen fraction. This allows us to unify and generalize results of
diophantine approximation from the literature
Balancedness of Arnoux-Rauzy and Brun words
We study balancedness properties of words given by the Arnoux-Rauzy and Brun
multi-dimensional continued fraction algorithms. We show that almost all Brun
words on 3 letters and Arnoux-Rauzy words over arbitrary alphabets are finitely
balanced; in particular, boundedness of the strong partial quotients implies
balancedness. On the other hand, we provide examples of unbalanced Brun words
on 3 letters
A remarkable sequence related to and
We prove that five ways to define entry A086377 in the On-Line Encyclopedia
of Integer Sequences do lead to the same integer sequence
Finite beta-expansions with negative bases
The finiteness property is an important arithmetical property of
beta-expansions. We exhibit classes of Pisot numbers having the
negative finiteness property, that is the set of finite -expansions
is equal to . For a class of numbers including the
Tribonacci number, we compute the maximal length of the fractional parts
arising in the addition and subtraction of -integers. We also give
conditions excluding the negative finiteness property
- âŠ