Characterization of test-sets for overlap-free morphisms
نویسندگان
چکیده
منابع مشابه
Characterization 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 ...
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...
متن کاملSemi-Commutativity Sets of Morphisms over Finitely Generated Free Monoids.dvi
The notion of a semi-commutativity set for word mappings was defined in [3] as an abstraction of a problem in cryptography. The notion is of special interest in case the mappings are morphisms. Then rather surprising constructions become possible. We investigate such constructions, paying special attention to exceptional values of inverse mappings. Some of our results bear a close relation to c...
متن کاملOptimal Test Sets for Context-Free Languages
A test set for a formal language (set of strings) L is a subset T of L such that for any two string homomorphisms f and g defined on L, if the restrictions of f and g on T are identical functions, then f and g are identical on the entire L. Previously, it was shown that there are context-free grammars for which smallest test sets are cubic in the size of the grammar, which gives a lower bound o...
متن کاملSeparable Morphisms of Simplicial Sets
We show that the class of separable morphisms in the sense of G. Janelidze and W. Tholen in the case of Galois structure of second order coverings of simplicial sets due to R. Brown and G. Janelidze coincides with the class of covering maps of simplicial sets. Introduction Separable morphisms were introduced in [3] by A. Carboni and G. Janelidze for lextensive categories. In the way of [3] one ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Discrete Applied Mathematics
سال: 1999
ISSN: 0166-218X
DOI: 10.1016/s0166-218x(99)00118-3