On Fully Idempotent Modules

A submodule N of a module M is idempotent if N = Hom(M, N)N. The module M is fully idempotent if every submodule of M is idempotent. We prove that over a commutative ring, cyclic idempotent submodules of any module are direct summands. Counterexamples are given to show that this result is not true in general. It is shown that over commutative Noetherian rings, the fully idempotent modules are precisely the semisimple modules. We also show that the commutative rings over which every module is fully idempotent are exactly the semisimple rings. Idempotent submodules of free modules are characterized.     

Stable t-structures and Homotopy Category of Strongly Copure Projective Modules

In this paper, we study the homotopy category of unbounded complexes of strongly copure projective modules with bounded relative homologies K~(∞,bscp)(SCP).We show that the existence of a right recollement of K~(∞,bscp)(SCP) with respect to K~(-,bscp)(SCP), K_(scpac)(SCP) and K~(∞,bscp)(SCP) has the homotopy category of strongly copure projective acyclic complexes as a triangulated subcategory in some case.     

T-Radicals in the Category of Modules

This paper deals with the class of idempotent radicals defined by means of a tensor product. Their effect on Abelian groups is described. We also establish their connection with attracting modules. Mathematics Subject Classification (2000) 18E40.     

Generic Idempotent Modules for a Finite Group

Let G be a finite group and k an algebraically closed field of characteristic p. Let F _U be the Rickard idempotent k G-module corresponding to the set U of subvarieties of the cohomology variety V _G which are not irreducible components. We show that F _U is a finite sum of generic modules corresponding to the irreducible components of V _G . In this context, a generic module is an indecomposable module of infinite length over k G but finite length as a module over its endomorphism ring.     

Idempotent and Nilpotent Submodules of Multiplication Modules

All rings are commutative with identity, and all modules are unital. The purpose of this article is to investigate multiplication von Neumann regular modules. For this reason we introduce the concept of nilpotent submodules generalizing nilpotent ideals and then prove that a faithful multiplication module is von Neumann regular if and only if it has no nonzero nilpotent elements and its Krull dimension is zero. We also give a new characterization for the radical of a submodule of a multiplication module and show in particular that the radical of any submodule of a Noetherian multiplication module is a finite intersection of prime submodules.     

Modules Coinvariant Under the Idempotent Endomorphisms of Their Covers

Siberian Mathematical Journal - We study the modules that are coinvariant under the idempotent endomorphisms of their covers. Some generalizations of discrete and continuous modules are introduced...     

Weakly Stable Modules

ABSTRACT

A new notion which is called weakly stable module is introduced in this article. It is a nontrivial generalization of the modules with endomorphism rings having stable range one. We deduce that weakly stable projective modules have the cancellation property, and so any commutative hereditary ring has the cancellation property, i.e., if R is a commutative hereditary ring, then for any R-modules B and C, R ⊕ B ? R ⊕ C implies B ? C.     

Rings of Idempotent Stable Range One

We show that in a ring of stable range 1, any (von Neumann) regular element is clean. Our main results also imply that any unit-regular ring has idempotent stable range 1 (and is therefore clean), and that a semilocal ring has idempotent stable range 1 if and only if it is semiperfect.     

I-Sequences in the Category of Modules

The notion of I-sequences (introduced by Green) in the category of modules over finite-dimensional algebras is developed in this paper and particularly used to give an alternative proof for the results of Knörr concerning the existence and properties of relative projective covers in the category of modules over group algebras.     

T-Radicals and E-Radicals in the Category of Modules

We introduce two classes of radicals by means of tensor product of modules and module homomorphisms and prove some properties of these radicals and their connection with attracting modules.     

Making the Category of Doi-Hopf Modules into a Braided Monoidal Category

We investigate how the category of Doi-Hopf modules can be made into a monoidal category. It suffices that the algebra and coalgebra in question are both bialgebras with some extra compatibility relation. We study tensor identies for monoidal categories of Doi-Hopf modules. Finally, we construct braidings on a monoidal category of Doi-Hopf modules. Our construction unifies quasitriangular and coquasitriangular Hopf algebras, and Yetter-Drinfel'd modules.     

构造群缠绕模范畴成为辫子张量范畴

该文研究了群缠绕模范畴怎样构造成张量范畴,给出的充分条件是要求群缠绕模中的代数和群余代数分别是双代数和半-Hopf群余代数,并满足一些相容条件.作者在张量群缠绕模范畴上构造了辫子.该文结果包括了拟三角和余拟三角Hopf代数(Hopf群余代数),Doi-Hopf群模等情况.     

Characterizing When the Category of Gorenstein Projective Modules is an Abelian Category

We find sufficient and necessary conditions for the category of Gorenstein projective modules of an artin algebra being an abelian category, and give another proof for the Auslander–Solberg correspondence which demonstrates the concrete form of the category of Gorenstein projective modules. Then we find a characterization for this category of Gorenstein projective modules. At last we give an example of this correspondence.     

缠绕模的辫子范畴

该文给出了缠绕模范畴成为辫子范畴的充分必要条件.     

Actions in the Category of Precrossed Modules in Lie Algebras

For any object L in the category of precrossed modules in Lie algebras PXLie, we construct the object Act(L), which we call the actor of this object. From this construction, we derive the notions of action, center, semidirect product, derivation, commutator, and abelian precrossed module in PXLie. We show that the notion of action is equivalent to the one given in semi-abelian categories, and Act(L) is the split extension classifier for L. In the case of a crossed module in Lie algebras we show how to recover its actor in the category of crossed modules from its actor in the category of precrossed modules.     

左三角范畴的稳定化和幂等完备

Let (CΩ△) be a left triangulated category with a fully faithful endofunctor.We show a triangle-equivalence (S(C),△) ～=(S(C),△),where (S(C)△,) denotes the stabilization of the idempotent completion of (C,△) and (S(C),△) denotes the idempotent completion of the stabilization of (C,△).     

Applications of the Category of Linear Complexes of Tilting Modules Associated with the Category

We use the category of linear complexes of tilting modules for the BGG category \mathfrakg\mathfrak{g}, to reprove in purely algebraic way several known results about obtained earlier by different authors using geometric methods. We also obtain several new results about the parabolic category .     

A Category of Restricted Modules for the Ovisenko-Roger Algebra

In this paper, we study a category of restricted modules for the Ovsienko-Roger algebra, which is an extension of the Virasoro algebra of its tensor density module of degree one. We construct and characterize simple modules in this category and give natural free field realizations of certain restricted modules using the Weyl vertex algebra.

     

左R-n模的范畴与Hom函子

正合列问题是同调代数的基本问题之一。在Abel范畴的同调代数中,先有核的概念再讨论正合列的概念。但,因n-予加法范畴不具有零对象,欲讨论正合列,对其引进拟核。本文对左R-n模的范畴_R~M_n~l讨论了与拟核相应的正合列;把Hom函子推广到_R~M_n~l上,讨论了它关于拟正合列、弱双积、正向系统的正向极限的不变性。至于对带终对象的范畴的正合列的讨论我们将在中进行。     

Anchor Maps and Stable Modules in Depth Two

An algebra extension A ∣ B is right depth two if its tensor-square is in the Dress category . We consider necessary conditions for right, similarly left, D2 extensions in terms of partial A-invariance of two-sided ideals in A contracted to the centralizer. Finite dimensional algebras extending central simple algebras are shown to be depth two. Following P. Xu, left and right bialgebroids over a base algebra R may be defined in terms of anchor maps, or representations on R. The anchor maps for the bialgebroids and over the centralizer R = C _A (B) are the modules _S R and R _T studied in Kadison (J. Alg. & Appl., 2005, preprint), Kadison (Contemp. Math., 391: 149–156, 2005), and Kadison and Külshammer (Commun. Algebra, 34: 3103–3122, 2006), which provide information about the bialgebroids and the extension (Kadison, Bull. Belg. Math. Soc. Simon Stevin, 12: 275–293, 2005). The anchor maps for the Hopf algebroids in Khalkhali and Rangipour (Lett. Math. Phys., 70: 259–272, 2004) and Kadison (2005, preprint) reverse the order of right multiplication and action by a Hopf algebra element, and lift to the isomorphism in Van Oystaeyen and Panaite (Appl. Categ. Struct., 2006, in press). We sketch a theory of stable A-modules and their endomorphism rings and generalize the smash product decomposition in Kadison (Proc. Am. Math. Soc., 131: 2993–3002, 2003 Prop. 1.1) to any A-module. We observe that Schneider’s coGalois theory in Schneider (Isr. J. Math., 72: 167–195, 1990) provides examples of codepth two, such as the quotient epimorphism of a finite dimensional normal Hopf subalgebra. A homomorphism of finite dimensional coalgebras is codepth two if and only if its dual homomorphism of algebras is depth two.