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An analogue of the Duistermaat-van der Kallen theorem for group algebras

Wenhua Zhao, Roel Willems (2012)

Open Mathematics

Let G be a group, R an integral domain, and V G the R-subspace of the group algebra R[G] consisting of all the elements of R[G] whose coefficient of the identity element 1G of G is equal to zero. Motivated by the Mathieu conjecture [Mathieu O., Some conjectures about invariant theory and their applications, In: Algèbre non Commutative, Groupes Quantiques et Invariants, Reims, June 26–30, 1995, Sémin. Congr., 2, Société Mathématique de France, Paris, 1997, 263–279], the Duistermaat-van der Kallen...

Bases of minimal elements of some partially ordered free abelian groups

Pavel Příhoda (2003)

Commentationes Mathematicae Universitatis Carolinae

In the present paper, we will show that the set of minimal elements of a full affine semigroup A 0 k contains a free basis of the group generated by A in k . This will be applied to the study of the group K 0 ( R ) for a semilocal ring R .

Behavior of countably generated pure-projective modules.

Goro Azumaya (1992)

Publicacions Matemàtiques

We first prove that every countably presented module is a pure epimorphic image of a countably generated pure-projective module, and by using this we prove that if every countably generated pure-projective module is pure-injective then every module is pure-injective, while if in any countably generated pure-projective module every countably generated pure-projective pure submodule is a direct summand then every module is pure-projective.

Comultiplication modules over a pullback of Dedekind domains

Reza Ebrahimi Atani, Shahabaddin Ebrahimi Atani (2009)

Czechoslovak Mathematical Journal

First, we give complete description of the comultiplication modules over a Dedekind domain. Second, if R is the pullback of two local Dedekind domains, then we classify all indecomposable comultiplication R -modules and establish a connection between the comultiplication modules and the pure-injective modules over such domains.

Costable rings

Tomáš Kepka (1974)

Commentationes Mathematicae Universitatis Carolinae

Countably thick modules

Ali Abdel-Mohsen, Mohammad Saleh (2005)

Archivum Mathematicum

The purpose of this paper is to further the study of countably thick modules via weak injectivity. Among others, for some classes of modules in σ [ M ] we study when direct sums of modules from satisfies a property in σ [ M ] . In particular, we get characterization of locally countably thick modules, a generalization of locally q.f.d. modules.

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