Positive varieties and infinite words
Résumé
Carrying on the work of Arnold, Pécuchet and Perrin, Wilke has obtained a counterpart of Eilenberg's variety theorem for finite and infinite words. In this paper, we extend this theory for classes of languages that are closed under union and intersection, but not necessarily under complement. As an example, we give a purely algebraic haracterization of various classes of recognizable sets defined by topological properties (open, closed, F? and G?) or by combinatorial properties.
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