Associative rings and the Whitehead property of modules [Abstract of thesis]
Auslander-Reiten components for concealed-canonical algebras
Auslander-Reiten triangles in derived categories.
Automorphism liftable modules
We introduce the notion of an automorphism liftable module and give a characterization to it. We prove that category equivalence preserves automorphism liftable. Furthermore, we characterize semisimple rings, perfect rings, hereditary rings and quasi-Frobenius rings by properties of automorphism liftable modules. Also, we study automorphism liftable modules with summand sum property (SSP) and summand intersection property (SIP).
Automorphisms and f-simplicity in skew polynomial rings
Bases of minimal elements of some partially ordered free abelian groups
In the present paper, we will show that the set of minimal elements of a full affine semigroup contains a free basis of the group generated by in . This will be applied to the study of the group for a semilocal ring .
Behavior of countably generated pure-projective modules.
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.
Bemerkungen zu einem Satz von L. A. Skornjakov über projektive Abbildung von Moduln
Berechnung der Gelfand-Kirillov-Dimension bei induzierten Darstellungen.
Bicovariant differential calculi and cross products on braided Hopf algebras
In a braided monoidal category C we consider Hopf bimodules and crossed modules over a braided Hopf algebra H. We show that both categories are equivalent. It is discussed that the category of Hopf bimodule bialgebras coincides up to isomorphism with the category of bialgebra projections over H. Using these results we generalize the Radford-Majid criterion and show that bialgebra cross products over the Hopf algebra H are precisely described by H-crossed module bialgebras. In specific braided monoidal...
Bi-ideals in k-regular and intra k-regular semirings
Here we introduce the k-bi-ideals in semirings and the intra k-regular semirings. An intra k-regular semiring S is a semiring whose additive reduct is a semilattice and for each a ∈ S there exists x ∈ S such that a + xa²x = xa²x. Also it is a semiring in which every k-ideal is semiprime. Our aim in this article is to characterize both the k-regular semirings and intra k-regular semirings using of k-bi-ideals.
Bipartite coalgebras and a reduction functor for coradical square complete coalgebras
Let C be a coalgebra over an arbitrary field K. We show that the study of the category C-Comod of left C-comodules reduces to the study of the category of (co)representations of a certain bicomodule, in case C is a bipartite coalgebra or a coradical square complete coalgebra, that is, C = C₁, the second term of the coradical filtration of C. If C = C₁, we associate with C a K-linear functor that restricts to a representation equivalence , where is a coradical square complete hereditary bipartite...
Bound quivers of three-separate stratified posets, their Galois coverings and socle projective representations
A class of stratified posets is investigated and their incidence algebras are studied in connection with a class of non-shurian vector space categories. Under some assumptions on we associate with a bound quiver (Q, Ω) in such a way that . We show that the fundamental group of (Q, Ω) is the free group with two free generators if is rib-convex. In this case the universal Galois covering of (Q, Ω) is described. If in addition is three-partite a fundamental domain of this covering is...
Bounded Picard groups
Bounds for the homological dimensions of pullbacks.
Calabi-Yau stable module categories of finite type
We describe the stable module categories of the self-injective finite-dimensional algebras of finite representation type over an algebraically closed field which are Calabi-Yau (in the sense of Kontsevich).
Cartan desompositions and BGG-resolutions.
Cartan matrices of selfinjective algebras of tubular type
The Cartan matrix of a finite dimensional algebra A is an important combinatorial invariant reflecting frequently structural properties of the algebra and its module category. For example, one of the important features of the modular representation theory of finite groups is the nonsingularity of Cartan matrices of the associated group algebras (Brauer’s theorem). Recently, the class of all tame selfinjective algebras having simply connected Galois coverings and the stable Auslander-Reiten quiver...
Categorical methods in graded ring theory.
Let G be a group, R a G-graded ring and X a right G-set. We study functors between categories of modules graded by G-sets, continuing the work of [M]. As an application we obtain generalizations of Cohen-Montgomery Duality Theorems by categorical methods. Then we study when some functors introduced in [M] (which generalize some functors ocurring in [D1], [D2] and [NRV]) are separable. Finally we obtain an application to the study of the weak dimension of a group graded ring.
Centralizer near-rings acting on SE-groups.