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Monomial right ideals and the Hilbert series of noncommutative modules. (English) Zbl 1349.16095
Summary: In this paper we present a procedure for computing the rational sum of the Hilbert series of a finitely generated monomial right module $$N$$ over the free associative algebra $$\mathbb{K} \langle x_1, \ldots, x_n \rangle$$. We show that such procedure terminates, that is, the rational sum exists, when all the cyclic submodules decomposing $$N$$ are annihilated by monomial right ideals whose monomials define regular formal languages. The method is based on the iterative application of the colon right ideal operation to monomial ideals which are given by an eventual infinite basis. By using automata theory, we prove that the number of these iterations is a minimal one. In fact, we have experimented efficient computations with an implementation of the procedure in Maple which is the first general one for noncommutative Hilbert series.

##### MSC:
 16Z05 Computational aspects of associative rings (general theory) 16P90 Growth rate, Gelfand-Kirillov dimension 05A15 Exact enumeration problems, generating functions
##### Keywords:
Hilbert series; noncommutative modules; automata
##### Software:
Maple; SINGULAR; ncHilb; Letterplace
Full Text:
##### References:
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