A1 Refereed original research article in a scientific journal
On the unavoidability of k-abelian squares in pure morphic words
Authors: Huova Mari, Karhumäki Juhani
Publisher: University of Waterloo
Publication year: 2013
Journal: Journal of Integer Sequences
Article number: 13.2.9
Volume: 16
Issue: 2
First page : 1
Last page: 11
Number of pages: 11
Web address : https://cs.uwaterloo.ca/journals/JIS/VOL16/Huova/huova2.html
We consider a recently defined notion of k-abelian equivalence of words by concentrating on avoidability problems. The equivalence class of a word depends on the number of occurrences of different factors of length k for a fixed natural number k and the prefix of the word. We show that over a ternary alphabet, k-abelian squares cannot be avoided in pure morphic words for any natural number k. Nevertheless, computational experiments support the conjecture that even 3-abelian squares can be avoided over a ternary alphabet. This illustrates that the simple but widely used method to produce infinite words by iterating a single morphism is not powerful enough with k-abelian avoidability questions.