Pattern avoidance is an important topic in combinatorics on words which dates back to the beginning of the twentieth century when Thue constructed an infinite word over a ternary alphabet that avoids squares, i.e., a word with no two adjacent identical factors. This result finds applications in various algebraic contexts where more general patterns than squares are considered. On the other hand, Erdős raised the question as to whether there exists an infinite word that avoids abelian squares, i.e., a word with no two adjacent factors being permutations of one another. Although this question was answered affirmately years later, knowledge of abelian pattern avoidance is rather limited. Recently, (abelian) pattern avoidance was initiated in the more general framework of partial words, which allow for undefined positions called holes. In this paper, we show that any pattern p with n> 3 distinct variables of length at least 2n is abelian avoidable by a partial word with infinitely many holes, the bound on the length of p being tight. We complete the classification of all the binary and ternary patterns with respect to non-trivial abelian avoidability, in which no variable can be substituted by only one hole. We also investigate the abelian avoidability indices of the binary and ternary patterns.
Mots clés : combinatorics on words, partial words, abelian powers, patterns, abelian patterns, avoidable patterns, avoidability index
@article{ITA_2014__48_3_315_0,
author = {Blanchet-Sadri, F. and De Winkle, Benjamin and Simmons, Sean},
title = {Abelian pattern avoidance in partial words},
journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
pages = {315--339},
publisher = {EDP-Sciences},
volume = {48},
number = {3},
year = {2014},
doi = {10.1051/ita/2014014},
mrnumber = {3302491},
zbl = {1297.68190},
language = {en},
url = {http://www.numdam.org/articles/10.1051/ita/2014014/}
}
TY - JOUR AU - Blanchet-Sadri, F. AU - De Winkle, Benjamin AU - Simmons, Sean TI - Abelian pattern avoidance in partial words JO - RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications PY - 2014 SP - 315 EP - 339 VL - 48 IS - 3 PB - EDP-Sciences UR - http://www.numdam.org/articles/10.1051/ita/2014014/ DO - 10.1051/ita/2014014 LA - en ID - ITA_2014__48_3_315_0 ER -
%0 Journal Article %A Blanchet-Sadri, F. %A De Winkle, Benjamin %A Simmons, Sean %T Abelian pattern avoidance in partial words %J RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications %D 2014 %P 315-339 %V 48 %N 3 %I EDP-Sciences %U http://www.numdam.org/articles/10.1051/ita/2014014/ %R 10.1051/ita/2014014 %G en %F ITA_2014__48_3_315_0
Blanchet-Sadri, F.; De Winkle, Benjamin; Simmons, Sean. Abelian pattern avoidance in partial words. RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications, Tome 48 (2014) no. 3, pp. 315-339. doi : 10.1051/ita/2014014. http://www.numdam.org/articles/10.1051/ita/2014014/
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