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arXiv 0907.0206math.NTmath.DS
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具有纯周期$β$ -展开的有理数

Rational numbers with purely periodic $β$-expansion

Boris Adamczewski, Christiane Frougny, Anne Siegel, Wolfgang Steiner

摘要:

我们研究实数$β$与好奇的性质,$β$ -扩展的所有足够小的正有理数是纯周期的。众所周知,这样的实数必须是皮索数,皮索数是它们生成的数域的单位。我们完成已知的结果,由于秋山的特点代数数的程度3,享受这一属性。这扩展了Schmidt、Hama和Imahashi在2度情形下的结果。令$γ(β)$表示$(0,1)$中实数$c$的上确界,使得所有小于$c$的正有理数都有纯周期$β$ -展开式。证明了对于一类含有最小Pisot数$η$的三次Pisot单位元,$γ(β)$是无理数.这一结果是由Akiyama和Scheicher的观察所激发的,即$γ(η)=0.666 666 666 086 ...$令人惊讶地接近2/3。

英文摘要:

We study real numbers $β$ with the curious property that the $β$-expansion of all sufficiently small positive rational numbers is purely periodic. It is known that such real numbers have to be Pisot numbers which are units of the number field they generate. We complete known results due to Akiyama to characterize algebraic numbers of degree 3 that enjoy this property. This extends results previously obtained in the case of degree 2 by Schmidt, Hama and Imahashi. Let $γ(β)$ denote the supremum of the real numbers $c$ in $(0,1)$ such that all positive rational numbers less than $c$ have a purely periodic $β$-expansion. We prove that $γ(β)$ is irrational for a class of cubic Pisot units that contains the smallest Pisot number $η$. This result is motivated by the observation of Akiyama and Scheicher that $γ(η)=0.666 666 666 086 ...$ is surprisingly close to 2/3.

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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