Displaying similar documents to “The globals of pseudovarieties of ordered semigroups containing B2 and an application to a problem proposed by Pin”

Hypercyclicity of Semigroups is a Very Unstable Property

W. Desch, W. Schappacher (2008)

Mathematical Modelling of Natural Phenomena

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Hypercyclicity of -semigroups is a very unstable property: We give examples to show that adding arbitrary small constants or a bounded rank one operator to the generator of a hypercyclic semigroup can destroy hypercyclicity. Also the limit of hypercyclic semigroups (even in operator norm topology) need not be hypercyclic, and a hypercyclic semigroup can be the limit of nonhypercyclic ones. Hypercyclicity is not inherited by the Yosida approximations. Finally, the restriction...

Strongly locally testable semigroups with commuting idempotents and related languages

Carla Selmi (2010)

RAIRO - Theoretical Informatics and Applications

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If we consider words over the alphabet which is the set of all elements of a semigroup , then such a word determines an element of : the product of the letters of the word. is strongly locally testable if whenever two words over the alphabet have the same factors of a fixed length , then the products of the letters of these words are equal. We had previously proved [19] that the syntactic semigroup of a rational language is strongly locally testable if and only if is both locally...

On the decidability of semigroup freeness

Julien Cassaigne, Francois Nicolas (2012)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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This paper deals with the decidability of semigroup freeness. More precisely, the freeness problem over a semigroup is defined as: given a finite subset  ⊆ , decide whether each element of has at most one factorization over . To date, the decidabilities of the following two freeness problems have been closely examined. In 1953, Sardinas and Patterson proposed a now famous algorithm for the freeness problem over the free monoids. In 1991, Klarner, Birget and Satterfield proved the undecidability...

On the decidability of semigroup freeness

Julien Cassaigne, Francois Nicolas (2012)

RAIRO - Theoretical Informatics and Applications

Similarity:

This paper deals with the decidability of semigroup freeness. More precisely, the freeness problem over a semigroup is defined as: given a finite subset  ⊆ , decide whether each element of has at most one factorization over . To date, the decidabilities of the following two freeness problems have been closely examined. In 1953, Sardinas and Patterson proposed a now famous algorithm for the freeness problem over the free...