EXISTENCE OF AN INFINITE TERNARY 64-ABELIAN SQUARE-FREE WORD
: Mari Huova
Publisher: EDP SCIENCES S A
: 2014
: RAIRO: Informatique Théorique et Applications / RAIRO: Theoretical Informatics and Applications
: RAIRO-THEORETICAL INFORMATICS AND APPLICATIONS
: RAIRO-THEOR INF APPL
: 48
: 3
: 307
: 314
: 8
: 0988-3754
DOI: https://doi.org/10.1051/ita/2014012
We consider a recently defined notion of k-abelian equivalence of words by concentrating on avoidance problems. The equivalence class of a word depends on the numbers of occurrences of different factors of length k for a fixed natural number k and the prefix of the word. We have shown earlier 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 ternary alphabets. In this paper we establish the first avoidance result showing that by choosing k to be large enough we have an infinite k-abelian square-free word over three letter alphabet. In addition, this word can be obtained as a morphic image of a pure morphic word.