Title
Characteristic Sturmian words are extremal for the Critical Factorization Theorem
Abstract
We prove that characteristic Sturmian words are extremal for the Critical Factorization Theorem (CFT) in the following sense. If p"x(n) denotes the local period of an infinite word x at point n, we prove that x is a characteristic Sturmian word if and only if p"x(n) is smaller than or equal to n+1 for all n=1 and it is equal to n+1 for infinitely many integers n. This result is extremal with respect to the CFT since a consequence of the CFT is that, for any infinite recurrent word x, either the function p"x is bounded, and in such a case x is periodic, or p"x(n)=n+1 for infinitely many integers n. As a byproduct of the techniques used in the paper we extend a result of Harju and Nowotka (2002) in [18] stating that any finite Fibonacci word f"n,n=5, has only one critical point. Indeed we determine the exact number of critical points in any finite standard Sturmian word.
Year
DOI
Venue
2012
10.1016/j.tcs.2012.03.012
Theor. Comput. Sci.
Keywords
DocType
Volume
infinite word,characteristic Sturmian word,point n,Critical Factorization Theorem,integers n,Characteristic Sturmian word,function p,finite standard Sturmian word,finite Fibonacci word,infinite recurrent word,critical point
Journal
454,
ISSN
Citations 
PageRank 
0304-3975
6
0.64
References 
Authors
11
2
Name
Order
Citations
PageRank
Filippo Mignosi156999.71
Antonio Restivo2697107.05