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arXiv 1809.08690math.NT
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几乎贝蒂分区

Almost Beatty Partitions

A. J. Hildebrand, Junxian Li, Xiaomin Li, Yun Xie

摘要:

给定$0<α<1$,密度$α$的贝蒂序列是序列$B_α=(\lfloor n/α\rfloor)_{n\in\mathbb{N}}$。Beatty定理指出,如果$α,β$是具有$α+β=1$的无理数,则Beatty序列$B_α$和$B_β$划分正整数,即每个正整数恰好属于这两个序列之一。另一方面,Uspensky表明,这个结果完全分解为三个(或更多)序列的分区:不存在一个单一的三重$(α,β,γ)$,使贝蒂序列$B_α,B_β,B_γ$分区的正整数。在本文中,我们考虑的问题,如何接近我们可以来一个三部分贝蒂分区考虑“几乎”贝蒂序列,即序列,代表小扰动的“确切”贝蒂序列。我们首先刻画所有的情况下,存在一个分区成两个确切的Beatty序列和一个几乎Beatty序列与给定的密度,我们确定的近似误差。然后,我们给出了两个一般的建设,产生分区成一个确切的Beatty序列和两个几乎Beatty序列与规定的密度,我们确定在这些建设的近似误差。最后,我们表明,在许多情况下,这些建设是最好的可能的意义上说,他们产生最接近的三部分贝蒂分区。

英文摘要:

Given $0<α<1$, the Beatty sequence of density $α$ is the sequence $B_α=(\lfloor n/α\rfloor)_{n\in\mathbb{N}}$. Beatty's theorem states that if $α,β$ are irrational numbers with $α+β=1$, then the Beatty sequences $B_α$ and $B_β$ partition the positive integers, that is, each positive integer belongs to exactly one of these two sequences. On the other hand, Uspensky showed that this result breaks down completely for partitions into three (or more) sequences: There does not exist a single triple $(α,β,γ)$ such that the Beatty sequences $B_α,B_β,B_γ$ partition the positive integers. In this paper we consider the question of how close we can come to a three-part Beatty partition by considering "almost" Beatty sequences, that is, sequences that represent small perturbations of an "exact" Beatty sequence. We first characterize all cases in which there exists a partition into two exact Beatty sequences and one almost Beatty sequence with given densities, and we determine the approximation error involved. We then give two general constructions that yield partitions into one exact Beatty sequence and two almost Beatty sequences with prescribed densities, and we determine the approximation error in these constructions. Finally, we show that in many situations these constructions are best-possible in the sense that they yield the closest approximation to a three-part Beatty partition.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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