A general form of non-Frobenius self-injective algebras
Applying the classical work of Nakayama [Ann. of Math. 40 (1939)], we exhibit a general form of non-Frobenius self-injective finite-dimensional algebras over a field.
A Generalization of Baer's Lemma
There is a classical result known as Baer’s Lemma that states that an -module is injective if it is injective for . This means that if a map from a submodule of , that is, from a left ideal of to can always be extended to , then a map to from a submodule of any -module can be extended to ; in other words, is injective. In this paper, we generalize this result to the category consisting of the representations of an infinite line quiver. This generalization of Baer’s Lemma...
A generalization of Ulm subgroups
A new proof of Gabriel's Lemma.
A note on block triangular presentations of rings and finitistic dimension
A note on quasitilted algebras
We provide a characterization of artin algebras without chains of nonzero homomorphisms between indecomposable finitely generated modules starting with an injective module and ending with a projective module.
A Note on the Structure of Injective Diagrams.
A note on tilting sequences
We discuss the existence of tilting modules which are direct limits of finitely generated tilting modules over tilted algebras.
A partition formula for Fibonacci numbers.
A remark concerning commutativity modulo radical in Banach algebras
A remark on decomposable modules.
A remark on quiver varieties and Weyl groups
In this paper we define an action of the Weyl group on the quiver varieties with generic .
A Remark on tilting theory and DG algebras.
A splitting theorem for multipeak path algebras
A theorem on direct products of Slender modules
Abelian group pairs having a trivial coGalois group
Torsion-free covers are considered for objects in the category Objects in the category are just maps in -Mod. For we find necessary and sufficient conditions for the coGalois group associated to a torsion-free cover, to be trivial for an object in Our results generalize those of E. Enochs and J. Rado for abelian groups.
Abelian groups which have trivial absolute coGalois group
In this article we characterize those abelian groups for which the coGalois group (associated to a torsion free cover) is equal to the identity.
Actions of parabolic subgroups in GL_n on unipotent normal subgroups and quasi-hereditary algebras
Let R be a parabolic subgroup in . It acts on its unipotent radical and on any unipotent normal subgroup U via conjugation. Let Λ be the path algebra of a directed Dynkin quiver of type with t vertices and B a subbimodule of the radical of Λ viewed as a Λ-bimodule. Each parabolic subgroup R is the group of automorphisms of an algebra Λ(d), which is Morita equivalent to Λ. The action of R on U can be described using matrices over the bimodule B. The advantage of this description is that each...
Additive functions for quivers with relations
Additive functions for quivers with relations extend the classical concept of additive functions for graphs. It is shown that the concept, recently introduced by T. Hübner in a special context, can be defined for different homological levels. The existence of such functions for level 2 resp. ∞ relates to a nonzero radical of the Tits resp. Euler form. We derive the existence of nonnegative additive functions from a family of stable tubes which stay tubes in the derived category, we investigate when...
Additive functions on trees
The motivation for considering positive additive functions on trees was a characterization of extended Dynkin graphs (see I. Reiten [R]) and applications of additive functions in representation theory (see H. Lenzing and I. Reiten [LR] and T. Hübner [H]). We consider graphs equipped with integer-valued functions, i.e. valued graphs (see also [DR]). Methods are given for constructing additive functions on valued trees (in particular on Euclidean graphs) and for characterizing...