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Difference between two floor functions
DOI:10.1007/s00605-026-02173-7.png)
Abstract
En 中文
In this paper, we confirm several conjectures of Benyi and Curgus related to the description of the set Range(alpha) attained by the differences of two floor functions [alpha(2)n] and [alpha [alpha n]], where alpha is a fixed positive number and n runs through all positive integers. In particular, we show that for each irrational number alpha > 0 the set Range(alpha) is the largest possible and takes all integral values between 0 and [alpha ]+1 except possibly for some quadratic algebraic numbers alpha > 1 when Range(alpha) can be smaller and take only integral values between 1 and [alpha]. Moreover, for every quadratic algebraic number alpha > 0, we explicitly determine the set Range(alpha) as well. In both cases, t = 0 and t = [alpha] + 1, we give explicit conditions describing whether t is or is not in Range(alpha). Those conditions are given in terms of the coefficients u, v of the minimal polynomial x(2)-ux-v E Q[x] of alpha over Q. All these results allow us to determine the set Range(alpha) explicitly for every irrational number alpha > 0. We also describe all the cases when Range(alpha) is a singleton set.
Keywords:
Kronecker's approximation theorem
Density
Distribution modulo 1
Quadratic irrationality

