منابع مشابه
On Morphisms Preserving Primitive Words
A word is called primitive if it cannot be expressed as the power of another word. Morphisms preserving primitive words are investigated. Similarly to the word case, each square-free morphism is a primitive morphism but the converse does not hold. A precise characterization of primitive morphisms is provided in terms of pure codes. An easily testable characterization is given for uniform morphi...
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Let g and h be binary morphisms defined on {a, b}∗, and let g be periodic and h nonperiodic. It is well known that their equality language is generated by at most one nonempty word. Suppose |h(b)| ≥ |h(a)|. We show that then the equality word is equal to aba , with i, j ≥ 0. Binary equality sets are the simplest nontrivial equality languages. Nevertheless, their full description is still not kn...
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We present an algorithm which produces, in some cases, infinite words avoiding both large fractional repetitions and a given set of finite words. We use this method to show that all the ternary patterns whose avoidability index was left open in Cassaigne’s thesis are 2-avoidable. We also prove that there exist exponentially many 7 4 + -free ternary words and 7 5 + -free 4-ary words. Finally we ...
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ژورنال
عنوان ژورنال: European Journal of Combinatorics
سال: 2020
ISSN: 0195-6698
DOI: 10.1016/j.ejc.2020.103160