In linear algebra, a linear relation, or simply relation, between elements of a vector space or a module is a linear equation that has these elements as a solution.
More precisely, if are elements of a (left) module M over a ring R (the case of a vector space over a field is a special case), a relation between is a sequence of elements of R such that
The relations between form a module. One is generally interested in the case where is a generating set of a finitely generated module M, in which case the module of the relations is often called a syzygy module of M. The syzygy module depends on the choice of a generating set, but it is unique up to the direct sum with a free module. That is, if and are syzygy modules corresponding to two generating sets of the same module, then they are stably isomorphic, which means that there exist two free modules and such that and are isomorphic.
Higher order syzygy modules are defined recursively: a first syzygy module of a module M is simply its syzygy module. For k > 1, a kth syzygy module of M is a syzygy module of a (k – 1)-th syzygy module. Hilbert's syzygy theorem states that, if is a polynomial ring in n indeterminates over a field, then every nth syzygy module is free. The case n = 0 is the fact that every finite dimensional vector space has a basis, and the case n = 1 is the fact that K[x] is a principal ideal domain and that every submodule of a finitely generated free K[x] module is also free.
The construction of higher order syzygy modules is generalized as the definition of free resolutions, which allows restating Hilbert's syzygy theorem as a polynomial ring in n indeterminates over a field has global homological dimension n.
If a and b are two elements of the commutative ring R, then (b, –a) is a relation that is said trivial. The module of trivial relations of an ideal is the submodule of the first syzygy module of the ideal that is generated by the trivial relations between the elements of a generating set of an ideal.
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Le théorème des syzygies est un important résultat mathématiques sur la théorie des anneaux, plus spécifiquement des anneaux de polynômes. Il joue également un rôle historique considérable, en ce qu'il a motivé et orienté le développement de la géométrie algébrique au début du . Il est dû au mathématicien allemand David Hilbert qui l'a démontré en 1890, posant avec le théorème de la base et le théorème des zéros les fondements de l'étude moderne des anneaux de polynômes.
In mathematics, and more specifically in homological algebra, a resolution (or left resolution; dually a coresolution or right resolution) is an exact sequence of modules (or, more generally, of s of an ), which is used to define invariants characterizing the structure of a specific module or object of this category. When, as usually, arrows are oriented to the right, the sequence is supposed to be infinite to the left for (left) resolutions, and to the right for right resolutions.
En mathématiques, les anneaux réguliers forment une classe d'anneaux très utile en géométrie algébrique. Ce sont des anneaux qui localement sont les plus proches possibles des anneaux de polynômes sur un corps. Soit un anneau local noethérien d'idéal maximal . Soit son espace tangent de Zariski qui est un espace vectoriel de dimension finie sur le corps résiduel . Cette dimension est minorée par la dimension de Krull de l'anneau . On dit que est régulier s'il y a égalité entre ces deux dimensions : Par le lemme de Nakayama, cela équivaut à dire que est engendré par éléments.
Let A be a nonnegatively graded connected algebra over a noncommutative separable k-algebra K, and let M be a bounded below graded right A-module. If we denote by T the -coalgebra , we know that there exists an -comodule structure on over T. The structure ...
In this article we introduce the notion of emphmulti-Koszul algebra for the case of a locally finite dimensional nonnegatively graded connected algebra, as a generalization of the notion of (generalized) Koszul algebras defined by R. Berger for homogeneous ...
2013
In [8] we introduced the notion of multi-Koszul algebra: it is an extension of the definition of generalized Koszul algebra given by R. Berger in [1] for homogeneous algebras (see also [7]) that can be applied to any nonnegatively graded connected algebra ...