Title
A characterization of eventual periodicity
Abstract
In this article, we show that the Kamae-Xue complexity function for an infinite sequence classifies eventual periodicity completely. We prove that an infinite binary word $x_1x_2 cdots $ is eventually periodic if and only if $Sigma(x_1x_2cdots x_n)/n^3$ has a positive limit, where $Sigma(x_1x_2cdots x_n)$ is the sum of the squares of all the numbers of appearance of finite words in $x_1 x_2 cdots x_n$, which was introduced by Kamae-Xue as a criterion of randomness in the sense that $x_1x_2cdots x_n$ is more random if $Sigma(x_1x_2cdots x_n)$ is smaller. In fact, it is known that the lower limit of $Sigma(x_1x_2cdots x_n) /n^2 $ is at least 3/2 for any sequence $x_1x_2 cdots$, while the limit exists as 3/2 almost surely for the $(1/2,1/2)$ product measure. For the other extreme, the upper limit of $Sigma(x_1x_2cdots x_n)/n^3$ is bounded by 1/3. There are sequences which are not eventually periodic but the lower limit of $Sigma(x_1x_2cdots x_n)/n^3$ is positive, while the limit does not exist.
Year
DOI
Venue
2014
10.1016/j.tcs.2015.02.039
Theoretical Computer Science
Keywords
DocType
Volume
combinatorics on words
Journal
581
Issue
ISSN
Citations 
C
0304-3975
0
PageRank 
References 
Authors
0.34
1
2
Name
Order
Citations
PageRank
Teturo Kamae1255.20
Dong Han Kim211918.40