On the ring of the variety of algebras over a ring
Let be a field and be the standard bigraded polynomial ring over . In this paper, we explicitly describe the structure of finitely generated bigraded “sequentially Cohen-Macaulay” -modules with respect to . Next, we give a characterization of sequentially Cohen-Macaulay modules with respect to in terms of local cohomology modules. Cohen-Macaulay modules that are sequentially Cohen-Macaulay with respect to are considered.
Let be a finite nonabelian group, its associated integral group ring, and its augmentation ideal. For the semidihedral group and another nonabelian 2-group the problem of their augmentation ideals and quotient groups is deal with. An explicit basis for the augmentation ideal is obtained, so that the structure of its quotient groups can be determined.
We study the problem of classifying triangulated categories with finite-dimensional morphism spaces and finitely many indecomposables over an algebraically closed field . We obtain a new proof of the following result due to Xiao and Zhu: the Auslander-Reiten quiver of such a category is of the form where is a disjoint union of simply-laced Dynkin diagrams and a weakly admissible group of automorphisms of . Then we prove that for ‘most’ groups , the category is standard,i.e.-linearly...
This paper is motivated by the question whether there is a nice structure theory of finitely generated modules over the Iwasawa algebra, i.e. the completed group algebra, of a -adic analytic group . For without any -torsion element we prove that is an Auslander regular ring. This result enables us to give a good definition of the notion of a pseudo-null -module. This is classical when for some integer , but was previously unknown in the non-commutative case. Then the category of -modules...
In this paper we consider completely decomposable torsion-free groups and we determine the subgroups which are ideals in every ring over such groups.