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arXiv 1102.5438math.COcs.DMcs.DSmath.NT
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等差数列上的非重复序列

Nonrepetitive sequences on arithmetic progressions

Jarosław Grytczuk, Jakub Kozik, Marcin Witkowski

摘要:

如果没有两个相邻的$S$块是相同的,则序列$S=s_{1}s_{2}..._{n}$是\emph{nonrepetitive}。1906年,Thue证明了在3元符号集上存在任意长的非重复序列。我们研究了涉及等差数列的非重复数列的推广。我们证明了,对于每个$k\geqslant 1$和每个$c\geqslant 1$存在任意长的序列,在最多的$(1+\frac{1}{c})k+18k^{c/c+1}$符号,其序列索引的等差数列从集合$\{1,2,...,k\}$是不重复的。这改进了先前在\cite{Grytczuk Rainbow}中获得的界限。我们的方法是基于最近在\cite{GrytczukKozikMicek},这是最初的灵感来自于一个建设性的证明Lovász本地引理由于Moser和Tardos \cite{MoserTardos}的技术。我们还讨论了一些相关的问题,可以成功地攻击这种方法。

英文摘要:

A sequence $S=s_{1}s_{2}..._{n}$ is \emph{nonrepetitive} if no two adjacent blocks of $S$ are identical. In 1906 Thue proved that there exist arbitrarily long nonrepetitive sequences over 3-element set of symbols. We study a generalization of nonrepetitive sequences involving arithmetic progressions. We prove that for every $k\geqslant 1$ and every $c\geqslant 1$ there exist arbitrarily long sequences over at most $(1+\frac{1}{c})k+18k^{c/c+1}$ symbols whose subsequences indexed by arithmetic progressions with common differences from the set $\{1,2,...,k\}$ are nonrepetitive. This improves a previous bound obtained in \cite{Grytczuk Rainbow}. Our approach is based on a technique introduced recently in \cite{GrytczukKozikMicek}, which was originally inspired by a constructive proof of the Lovász Local Lemma due to Moser and Tardos \cite{MoserTardos}. We also discuss some related problems that can be successfully attacked by this method.

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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