On Some Operators on Pseudovarieties
نویسنده
چکیده
Birkhoff’s theorem [1] asserts that a class of algebras of a given type τ : T → N is a variety if and only if it is closed under operation of passing to subalgebras, homomorphic images and also arbitrary direct products. Motivated by applications of the theory of automata Eilenberg and Schützenberger considered in [2], [3] classes of finite monoids closed under subalgebras, homomorphic images and finite products. These considerations led to the notion of a pseudovariety defined in [3] as follows:
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تاریخ انتشار 2005