منابع مشابه
A Characterization of Sturmian Morphisms
A one-sided infinite word is balanced if the difference of the number of occurrences of a letter in two factors of the same length never exceeds one. It is Sturmian if it is balanced and not ultimately periodic. Sturmian words have a long history. A clear exposition of early work by J. Bernoulli, Christoffel, and A. A. Markov is given in the book by Venkov [22]. The term "Sturmian" has been use...
متن کاملA Characterization of Overlap-Free Morphisms
We prove that a morphism h over a two-letter alphabet {a, b} is overlap-free, i.e., maps overlap-free words into overlap-free words, iff the word h(abbabaab) is overlap-free. As a consequence, we obtain a simple proof of the fact that the only infinite overlap-free words that can be obtained by iterating a morphism are the Thue-Morse sequence and its opposite. RLsumP Nous prouvons qu’un morphis...
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Let G be a discrete, torsion free group with a finite dimensional classifying space BG. We show that the existence of a γ-element for such G is a metric, that is, coarse, invariant of G. We also obtain results for groups with torsion. The method of proof involves showing that a group G possesses a γ-element if and only if a certain coarse (co)-assembly map is an isomorphism.
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In this paper, we prove that the category of crossed polymodules (i.e. crossed modules of polygroups) and their morphisms is finitely complete. We, therefore, generalize the group theoretical case of this completeness property of crossed modules.
متن کاملCharacterization of Test-sets for Overlap-free Morphisms
We give a characterization of all the sets X such that any morphism h on fa; bg is overlap-free ii for all x in X , h(x) is overlap-free. As a consequence, we observe the particular case X = fbbabaag which improves the previous characterization of Berstel-S e ebold 2]. R esum e Nous donnons une caract erisation de tous les ensembles X tels qu'un morphisme h sur fa; bg est sans chevauchement si ...
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ژورنال
عنوان ژورنال: Communications in Mathematical Physics
سال: 2009
ISSN: 0010-3616,1432-0916
DOI: 10.1007/s00220-008-0713-0