MODULES FOR WHICH EVERY SUBMODULE HAS A UNIQUE COCLOSURE

ABSTRACT

P. F. Smith studied modules in which every submodule has a unique closure and called them UC modules. In this paper we consider modules with the dual property viz., those in which every submodule has a unique coclosure and call such modules UCC modules. Unlike closures, a coclosure of a submodule of a module may not always exist and even if it exists, it may not be unique. We investigate the conditions under which a module is a UCC module. We prove that UCC modules are closed under factor modules and coclosed submodules. We also investigate their properties and their relation to non-cosingular modules, copolyform modules, and codimension modules. We end this paper with the dual of Smith's result on dimension modules.     

量子环面C-1上的一族Noether模

记C_-1为q=-1 的量子环面Lie代数. 本文以Laurent 多项式环C[x^±1] 为表示空间, 构造了C_-1上的一类Noether 但非Artin 的模, 并确定了它们的全部子模和商模以及它们之间的全体模同态,最后指出该模与A₁型loop代数忠实表示的关系.     

Characterizations of some rings with <Emphasis Type="Italic">C</Emphasis>-projective, <Emphasis Type="Italic">C</Emphasis>-(FP)-injective and <Emphasis Type="Italic">C</Emphasis>-flat modules

Let R be a commutative ring and C a semidualizing R-module. We investigate the relations between C-flat modules and C-FP-injective modules and use these modules and their character modules to characterize some rings, including artinian, noetherian and coherent rings.     

Symmetric and Exterior Powers, Linear Source Modules and Representations of Schur Superalgebras

We study modules for the general linear group (over an infinitefield of arbitrary characteristic) which are direct summandsof tensor products of exterior powers and symmetric powers ofthe natural module. These modules, which we call listing modules,include the tilting modules and the injective modules for Schuralgebras. The modules are studied via their relationship tolinear source modules for symmetric groups on the one hand,and simple modules for Schur superalgebras on the other. Listingmodules are parametrized by certain pairs of partitions. Theyare used to describe, by generators and relations, the Grothendieckring of polynomial functors generated by the symmetric and exteriorpowers. We also (continuing work of J. Grabmeier) describe thevertices and sources of linear source modules for symmetricgroups. 2000 Mathematical Subject Classification: 20G05, 20C30.     

Cohomology theories based on Gorenstein injective modules

In this paper we study relative and Tate cohomology of modules of finite Gorenstein injective dimension. Using these cohomology theories, we present variations of Grothendieck local cohomology modules, namely Gorenstein and Tate local cohomology modules. By applying a sort of Avramov-Martsinkovsky exact sequence, we show that these two variations of local cohomology are tightly connected to the generalized local cohomology modules introduced by J. Herzog. We discuss some properties of these modules and give some results concerning their vanishing and non-vanishing.

     

On 𝒦-Nonsingular Modules and Applications

We introduce the notion of 𝒦-nonsingularity of a module and show that the class of 𝒦-nonsingular modules properly contains the classes of nonsingular modules and of polyform modules. A necessary and sufficient condition is provided to ensure that this property is preserved under direct sums. Connections of 𝒦-nonsingular modules to their endomorphism rings are investigated. Rings for which all modules are 𝒦-nonsingular are precisely determined. Applications include a type theory decomposition for 𝒦-nonsingular extending modules and internal characterizations for 𝒦-nonsingular continuous modules which are of type I, type II, and type III, respectively.     

HIGH ORDER KÄHLER MODULES OF NONCOMMUTATIVE RING EXTENSIONS

We construct the high order Kähler modules of noncommutative ring extensions B/A and show their fundamental properties. Our Kähler modules represent not only high order left derivations for one-sided modules but also high order central derivations for bimodules, which are usual derivations. This new viewpoint enables us to prove new results which were not known even though B is an algebra over a commutative ring A. Our results are the decomposition of Kähler modules by an idempotent element, exact sequences of Kähler modules, the Kähler modules of factor rings, and the relation to separable extensions. In particular, our exact sequences of high order Kähler modules were not known even though B is commutative.     

Ideal Submodules Versus Ternary Ideals Versus Linking Ideals

We show that ideal submodules and closed ternary ideals in Hilbert modules are the same. We use this insight as a little peg on which to hang a little note about interrelations with other notions regarding Hilbert modules. In Section 3, we show that the ternary ideals (and equivalent notions) merit fully, in terms of homomorphisms and quotients, to be called ideals of (not necessarily full) Hilbert modules. The properties to be checked are intrinsically formulated for the modules (without any reference to the algebra over which they are modules) in terms of their ternary structure. The proofs, instead, are motivated from a third equivalent notion, linking ideals (Section 2), and a Theorem (Section 3) that all extends nicely to (reduced) linking algebras. As an application, in Section 4, we introduce ternary extensions of Hilbert modules and prove most of the basic properties (some new even for the known notion of extensions of Hilbert modules), by reducing their proof to the well-known analogue theorems about extensions of C^?–algebras. Finally, in Section 5, we propose several open problems that our method naturally suggests.

     

The degree of the Hilbert–Poincaré polynomial of PBW-graded modules

In this note, we study the Hilbert–Poincaré polynomials for the associated PBW-graded modules of simple modules for a simple complex Lie algebra. The computation of their degree can be reduced to modules of fundamental highest weight. We provide these degrees explicitly.     

Representations of pointed Hopf algebras and their Drinfel'd quantum doubles

We study representations of nontrivial liftings of nilpotent type of quantum linear spaces and their Drinfel'd quantum doubles. We construct a family of Verma-type modules in both cases and prove a parametrization theorem for simple modules. We compute the Loewy and socle series of Verma modules under a mild restriction on the datum of a lifting. We find bases and dimensions of simple modules.     

Verma type modules for toroidal lie algebras

We study the structure of imaginary Verma modules induced from the"natural"Borel subalgebra of a toroidal Lie algebra. In particular, we establish a criterion of irreducibility for imaginary Verma modules and describe their submodules and irreducible quotients. We also describe the structure of Verma type modules in the case of sl(2)-toroidal Lie algebra over two variables.     

Stable anti-Yetter–Drinfeld modules

We define and study a class of entwined modules (stable anti-Yetter–Drinfeld modules) that serve as coefficients for the Hopf-cyclic homology and cohomology. In particular, we explain their relationship with Yetter–Drinfeld modules and Drinfeld doubles. Among sources of examples of stable anti-Yetter–Drinfeld modules, we find Hopf–Galois extensions with a flipped version of the Miyashita–Ulbrich action. To cite this article: P.M. Hajac et al., C. R. Acad. Sci. Paris, Ser. I 338 (2004).     

Structure of T Modules and Restricted Duals: The Classical and the Quantum Case

Abstract

A concrete realization of Enright's T modules is obtained. This is used to show their self-duality. As a consequence, the restricted duals of Verma modules are also identified.     

On Multigraded Generalizations of Kirillov–Reshetikhin Modules

We study the category of $\mathbb Z^\ell$ -graded modules with finite-dimensional graded pieces for certain $\mathbb Z^\ell_+$ -graded Lie algebras. We also consider certain Serre subcategories with finitely many isomorphism classes of simple objects. We construct projective resolutions for the simple modules in these categories and compute the Ext groups between simple modules. We show that the projective covers of the simple modules in these Serre subcategories can be regarded as multigraded generalizations of Kirillov–Reshetikhin modules and give a recursive formula for computing their graded characters.     

伪内射模与主伪内射模

本文研究了伪内射模与主伪内射模,它们分别是拟内射模与PQ-内射模的推广．伪内射模是对偶于伪投射模的．我们讨论了伪内射模与主伪内射模的性质及其自同态环,并得到了自同态环的Jacobson根的若干性质．     

Global Weyl modules for the twisted loop algebra

We define global Weyl modules for twisted loop algebras and analyze their highest weight spaces, which are in fact isomorphic to Laurent polynomial rings in finitely many variables. We are able to show that the global Weyl module is a free module of finite rank over these rings. Furthermore we prove, that there exist injective maps from the global Weyl modules for twisted loop algebras into a direct sum of global Weyl modules for untwisted loop algebras. Relations between local Weyl modules for twisted and untwisted generalized current algebras are known; we provide for the first time a relation on global Weyl modules.     

Tree modules of the generalised Kronecker quiver

For coprime roots certain torus fixed points of the Kronecker moduli space are indecomposable tree modules. They are indecomposable representations of the regular m-tree and can be glued in order to get stable torus fixed points for every coprime root. Using their stability and the reflection functor we show that for arbitrary roots there exist indecomposable tree modules of the Kronecker quiver as factor modules of these torus fixed points.     

Modules over quantaloids: Applications to the isomorphism problem in algebraic logic and π-institutions

We solve the isomorphism problem in the context of abstract algebraic logic and of π-institutions, namely the problem of when the notions of syntactic and semantic equivalence among logics coincide. The problem is solved in the general setting of categories of modules over quantaloids. We introduce closure operators on modules over quantaloids and their associated morphisms. We show that, up to isomorphism, epis are morphisms associated with closure operators. The notions of (semi-)interpretability and (semi-)representability are introduced and studied. We introduce cyclic modules, and provide a characterization for cyclic projective modules as those having a g-variable. Finally, we explain how every π-institution induces a module over a quantaloid, and thus the theory of modules over quantaloids can be considered as an abstraction of the theory of π-institutions.