Subword complexity and power avoidance
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Date
2019-11-05
Authors
Shallit, Jeffrey
Shur, Arseny
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
We begin a systematic study of the relations between subword complexity of infinite words and their power avoidance. Among other things, we show that
–the Thue–Morse word has the minimum possible subword complexity over all overlap-free binary words and all (7/3)-power-free binary words, but not over all (7/3)+-power-free binary words;
–the twisted Thue–Morse word has the maximum possible subword complexity over all overlap-free binary words, but no word has the maximum subword complexity over all (7/3)-power-free binary words;
–if some word attains the minimum possible subword complexity over all square-free ternary words, then one such word is the ternary Thue word;
–the recently constructed 1-2-bonacci word has the minimum possible subword complexity over all symmetric square-free ternary words.
Description
The final publication is available at Elsevier via https://doi.org/10.1016/j.tcs.2018.09.010. © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Keywords
combinatorics on words, subword complexity, power-free word, critical exponent, Thue–Morse word