Displaying similar documents to “Some results on 𝒞 -varieties”

A conjecture on the concatenation product

Jean-Eric Pin, Pascal Weil (2001)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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In a previous paper, the authors studied the polynomial closure of a variety of languages and gave an algebraic counterpart, in terms of Mal’cev products, of this operation. They also formulated a conjecture about the algebraic counterpart of the boolean closure of the polynomial closure – this operation corresponds to passing to the upper level in any concatenation hierarchy. Although this conjecture is probably true in some particular cases, we give a counterexample in the general...

Imre Simon : an exceptional graduate student

Denis Thérien (2005)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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This short note reviews the main contributions of the Ph.D. thesis of Imre Simon. His graduate work had major impact on algebraic theory of automata and thirty years later we are in a good position to appreciate how sensitive he was in selecting good problems, and how clever in solving them!

Varieties of finite categories

Alex Weiss, Denis Therien (1986)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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Some results on -varieties

Jean-Éric Pin, Howard Straubing (2010)

RAIRO - Theoretical Informatics and Applications

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In an earlier paper, the second author generalized Eilenberg's variety theory by establishing a basic correspondence between certain classes of monoid morphisms and families of regular languages. We extend this theory in several directions. First, we prove a version of Reiterman's theorem concerning the definition of varieties by identities, and illustrate this result by describing the identities associated with languages of the form , where are distinct letters....

Regular languages definable by Lindström quantifiers

Zoltán Ésik, Kim G. Larsen (2003)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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In our main result, we establish a formal connection between Lindström quantifiers with respect to regular languages and the double semidirect product of finite monoids with a distinguished set of generators. We use this correspondence to characterize the expressive power of Lindström quantifiers associated with a class of regular languages.

Finite basis problem for 2-testable monoids

Edmond Lee (2011)

Open Mathematics

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A monoid S 1 obtained by adjoining a unit element to a 2-testable semigroup S is said to be 2-testable. It is shown that a 2-testable monoid S 1 is either inherently non-finitely based or hereditarily finitely based, depending on whether or not the variety generated by the semigroup S contains the Brandt semigroup of order five. Consequently, it is decidable in quadratic time if a finite 2-testable monoid is finitely based.