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arXiv 1207.4233math.COcs.DM
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林登词与斐波那契数

Lyndon words and Fibonacci numbers

Kalle Saari

摘要:

非字母林登词的一个基本属性是它们可以表示为两个较短的林登词的连接。这导致长度为n的林登字必须具有的不同林登因子的数目的朴素下界log_{2}(n)} + 1,但该界不是最优的。在本文中,我们证明了一个更准确的下界是log_{phi}(n)+ 1,其中phi表示黄金分割比(1 + sqrt{5})/2。我们表明,这个界限是最佳的,因为它是由斐波那契林登的话。然后我们引入一个映射L_x,它计算无限字x中长度不超过n的Lyndon因子的个数。我们证明了循环无穷字x是非周期的当且仅当L_x >= L_f,其中f是Fibonacci无穷字,等式当且仅当f在f的移位轨道闭包中.

英文摘要:

It is a fundamental property of non-letter Lyndon words that they can be expressed as a concatenation of two shorter Lyndon words. This leads to a naive lower bound log_{2}(n)} + 1 for the number of distinct Lyndon factors that a Lyndon word of length n must have, but this bound is not optimal. In this paper we show that a much more accurate lower bound is log_{phi}(n) + 1, where phi denotes the golden ratio (1 + sqrt{5})/2. We show that this bound is optimal in that it is attained by the Fibonacci Lyndon words. We then introduce a mapping L_x that counts the number of Lyndon factors of length at most n in an infinite word x. We show that a recurrent infinite word x is aperiodic if and only if L_x >= L_f, where f is the Fibonacci infinite word, with equality if and only if f is in the shift orbit closure of f.

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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