30 research outputs found
Quadratic automaton algebras and intermediate growth
We present an example of a quadratic algebra given by three generators and
three relations, which is automaton (the set of normal words forms a regular
language) and such that its ideal of relations does not possess a finite
Gr\"obner basis with respect to any choice of generators and any choice of a
well-ordering of monomials compatible with multiplication. This answers a
question of Ufnarovski.
Another result is a simple example (4 generators and 7 relations) of a
quadratic algebra of intermediate growth.Comment: To appear in Journal of Cobinatorial Algebr
Monomial right ideals and the Hilbert series of noncommutative modules
In this paper we present a procedure for computing the rational sum of the
Hilbert series of a finitely generated monomial right module over the free
associative algebra . We show that such
procedure terminates, that is, the rational sum exists, when all the cyclic
submodules decomposing 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.Comment: 15 pages, to appear in Journal of Symbolic Computatio
Graph products of spheres, associative graded algebras and Hilbert series
Given a finite, simple, vertex-weighted graph, we construct a graded
associative (non-commutative) algebra, whose generators correspond to vertices
and whose ideal of relations has generators that are graded commutators
corresponding to edges. We show that the Hilbert series of this algebra is the
inverse of the clique polynomial of the graph. Using this result it easy to
recognize if the ideal is inert, from which strong results on the algebra
follow. Non-commutative Grobner bases play an important role in our proof.
There is an interesting application to toric topology. This algebra arises
naturally from a partial product of spheres, which is a special case of a
generalized moment-angle complex. We apply our result to the loop-space
homology of this space.Comment: 19 pages, v3: elaborated on connections to related work, added more
citations, to appear in Mathematische Zeitschrif
Multigraded Hilbert Series of noncommutative modules
In this paper, we propose methods for computing the Hilbert series of
multigraded right modules over the free associative algebra. In particular, we
compute such series for noncommutative multigraded algebras. Using results from
the theory of regular languages, we provide conditions when the methods are
effective and hence the sum of the Hilbert series is a rational function.
Moreover, a characterization of finite-dimensional algebras is obtained in
terms of the nilpotency of a key matrix involved in the computations. Using
this result, efficient variants of the methods are also developed for the
computation of Hilbert series of truncated infinite-dimensional algebras whose
(non-truncated) Hilbert series may not be rational functions. We consider some
applications of the computation of multigraded Hilbert series to algebras that
are invariant under the action of the general linear group. In fact, in this
case such series are symmetric functions which can be decomposed in terms of
Schur functions. Finally, we present an efficient and complete implementation
of (standard) graded and multigraded Hilbert series that has been developed in
the kernel of the computer algebra system Singular. A large set of tests
provides a comprehensive experimentation for the proposed algorithms and their
implementations.Comment: 28 pages, to appear in Journal of Algebr
BERGMAN under MS-DOS and Anick's resolution
Noncommutative algebras, defined by the generators and relations, are considered. The definition and main results connected with the Gröbner basis, Hilbert series and Anick's resolution are formulated. Most attention is paid to universal enveloping algebras. Four main examples illustrate the main concepts and ideas. Algorithmic problems arising in the calculation of the Hilbert series are investigated. The existence of finite state automata, defining thebehaviour of the Hilbert series, is discussed. The extensions of the BERGMAN package for IBM PC compatible computers are described. A table is provided permitting a comparison of the effectiveness of the calculations in BERGMAN with the other systems
Noncommutative Grobner basis, Hilbert series, Anick's resolution and BERGMAN under MS-DOS
The definition and main results connected with Grцbner basis, Hilbert series and Anick's resolution are formulated. The method of the infinity behavior prediction of Grцbner basis in noncommutative case is presented. The extensions of BERGMAN package for IBM PC compatible computers are described
On the computation of Hilbert series and Poincare series for algebras with infinite Grobner bases
In this paper we present algorithms to compute finite state automata which, given any rational language, recognize the languages of normal words and n-chains. We also show how these automata can be used to compute the Hilbert series and Poincaré series for any algebra with a rational set of leading words of its minimal Gröbner basis
Non-commutative Gröbner Bases and Applications
Commutative Gröbner bases have a lot of applications in theory and practice, because they have many nice properties, they are computable, and there exist many efficient improvements of their computations. Non-commutative Gröbner bases also have many useful properties. However, applications of non-commutative Gröbner bases are rarely considered due to high complexity of computations. The purpose of this study was to improve the computation of non-commutative Gröbner bases and investigate the applications of non-commutative Gröbner bases. Gröbner basis theory in free monoid rings was carefully revised and Gröbner bases were precisely characterized in great detail. For the computations of Gröbner bases, the Buchberger Procedure was formulated. Three methods, say interreduction on obstructions, Gebauer-Möller criteria, and detecting redundant generators, were developed for efficiently improving the Buchberger Procedure. Further, the same approach was applied to study Gröbner basis theory in free bimodules over free monoid rings. The Buchberger Procedure was also formulated and improved in this setting. Moreover, J.-C. Faugere's F4 algorithm was generalized to this setting. Finally, many meaningful applications of non-commutative Gröbner bases were developed. Enumerating procedures were proposed to semi-decide some interesting undecidable problems. All the examples in the thesis were computed using the package gbmr of the computer algebra system ApCoCoA. The package was developed by the author. It contains dozens of functions for Gröbner basis computations and many concrete applications. The package gbmr and a collection of interesting examples are available at http://www.apcocoa.org/