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26
result(s) for
"Direct sum decompositions."
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Topologically Semiperfect Topological Rings
We define topologically semiperfect (complete, separated, right linear) topological rings and characterize them by equivalent conditions. We show that the endomorphism ring of a module, endowed with the finite topology, is topologically semiperfect if and only if the module is decomposable as an (infinite) direct sum of modules with local endomorphism rings. Then we study structural properties of topologically semiperfect topological rings and prove that their topological Jacobson radicals are strongly closed and the related topological quotient rings are topologically semisimple. For the endomorphism ring of a direct sum of modules with local endomorphism rings, the topological Jacobson radical is described explicitly as the set of all matrices of nonisomorphisms. Furthermore, we prove that, over a topologically semiperfect topological ring, all finitely generated discrete modules have projective covers in the category of modules, while all lattice-finite contramodules have projective covers in both the categories of modules and contramodules. We also show that the topological Jacobson radical of a topologically semiperfect topological ring is equal to the closure of the abstract Jacobson radical, and present a counterexample demonstrating that the topological Jacobson radical can be strictly larger than the abstract one. Finally, we discuss the problem of lifting idempotents modulo the topological Jacobson radical and the structure of projective contramodules for topologically semiperfect topological rings.
Journal Article
Least-Squared Mixed Variational Formulation Based on Space Decomposition for a Kind of Variable-Coefficient Fractional Diffusion Problems
In this paper, we decompose the fractional derivative space as the direct-sum of a fractional Sobolev space and a singular space spanned by
x
-
β
and then propose a
x
-
β
-independent mixed type variational formulation over the commonly used Sobolev spaces for a kind of variable-coefficient fractional diffusion equations, based on the least-squared techniques and the merits of the direct-sum decomposition. We then prove the existence and uniqueness of the variational formulation, show the equivalence between the variational formulation and the fractional diffusion equation and discuss the regularity of the solution to the equation with a general right hand side function. As a consequence, an easily-computed and optimal-order-convergent least-squared mixed finite element method is established. The optimal-order numerical analysis with supporting numerical experiments is also conducted.
Journal Article
(Co)isotropic Pairs in Poisson and Presymplectic Vector Spaces
We give two equivalent sets of invariants which classify pairs of coisotropic subspaces of finite-dimensional Poisson vector spaces. For this it is convenient to dualize; we work with pairs of isotropic subspaces of presymplectic vector spaces. We identify ten elementary types which are the building blocks of such pairs, and we write down a matrix, invertible over [...], which takes one 10-tuple of invariants to the other. [ProQuest: [...] denotes formulae omitted.]
Journal Article
Definition and Properties of Direct Sum Decomposition of Groups
In this article, direct sum decomposition of group is mainly discussed. In the second section, support of element of direct product group is defined and its properties are formalized. It is formalized here that an element of direct product group belongs to its direct sum if and only if support of the element is finite. In the third section, product map and sum map are prepared. In the fourth section, internal and external direct sum are defined. In the last section, an equivalent form of internal direct sum is proved. We referred to [23], [22], [8] and [18] in the formalization.
Journal Article
Direct-sum decompositions of modules with semilocal endomorphism rings
According to the classical Krull–Schmidt Theorem, any module of finite composition length decomposes as a direct sum of indecomposable modules in an essentially unique way, that is, unique up to isomorphism of the indecomposable summands and a permutation of the summands. Modules that do not have finite composition length can have completely different behaviors. In this survey, we consider in particular the case of the modules
M
R
whose endomorphism ring
E
:= End(
M
R
) is a semilocal ring, that is,
E
/
J
(
E
) is a semisimple artinian ring. For instance, modules of finite composition length have a semilocal endomorphism ring, but several other classes of modules also have a semilocal endomorphism ring, for example artinian modules, finite direct sums of uniserial modules, finitely generated modules over commutative semilocal rings, and finitely presented modules over arbitrary semilocal rings. Several interesting phenomena appear in these cases. For instance, modules with a semilocal endomorphism ring have very regular direct-sum decompositions into indecomposables, their direct summands can be described via lattices, and direct-sum decompositions into indecomposables (=uniserial submodules) of finite direct sums of uniserial modules are described via their monogeny classes and their epigeny classes up to two permutations of the factors.
Journal Article
Equivalent Expressions of Direct Sum Decomposition of Groups
In this article, the equivalent expressions of the direct sum decomposition of groups are mainly discussed. In the first section, we formalize the fact that the internal direct sum decomposition can be defined as normal subgroups and some of their properties. In the second section, we formalize an equivalent form of internal direct sum of commutative groups. In the last section, we formalize that the external direct sum leads an internal direct sum. We referred to [19], [18] [8] and [14] in the formalization.
Journal Article
Conservation Rules of Direct Sum Decomposition of Groups
In this article, conservation rules of the direct sum decomposition of groups are mainly discussed. In the first section, we prepare miscellaneous definitions and theorems for further formalization in Mizar [5]. In the next three sections, we formalized the fact that the property of direct sum decomposition is preserved against the substitutions of the subscript set, flattening of direct sum, and layering of direct sum, respectively. We referred to [14], [13] [6] and [11] in the formalization.
Journal Article
Definition and Properties of Direct Sum Decomposition of Groups1
In this article, direct sum decomposition of group is mainly discussed. In the second section, support of element of direct product group is defined and its properties are formalized. It is formalized here that an element of direct product group belongs to its direct sum if and only if support of the element is finite. In the third section, product map and sum map are prepared. In the fourth section, internal and external direct sum are defined. In the last section, an equivalent form of internal direct sum is proved. We referred to [23], [22], [8] and [18] in the formalization.
Journal Article
Model theory of modules, algebras and categories : International Conference Model Theory of Modules, Algebras and Categories, July 28-August 2, 2017, Ettore Majorana Foundation and Centre for Scientific Culture, Erice, Sicily, Italy
This volume contains the proceedings of the international conference Model Theory of Modules, Algebras and Categories, held from July 28-August 2, 2017, at the Ettore Majorana Foundation and Centre for Scientific Culture in Erice, Italy.Papers contained in this volume cover recent developments in model theory, module theory and category theory, and their intersection.
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