bluuebunny/crossref_metadata_2025 huggingface dataset:
Filter Rings Under Flat Base Change
Authors: Sahandi Parviz , Yassemi Siamak
Published: February 2014

Let φ: (R, 𝔪) → (S, 𝔫) be a flat local homomorphism of rings. In this paper, we prove: (1) If dim S/𝔪S > 0, then S is a filter ring if and only if R and k(𝔭) ⊗R𝔭 S𝔮 are Cohen–Macaulay for all 𝔮 ∈ Spec (S) \ {𝔫} and 𝔭= 𝔮 ∩ R, and S/𝔭S is catenary and equidimensional for all minimal prime ideals 𝔭 of R. (2) If dim S/𝔪S = 0, then S is a filter ring if and only if R is a filter ring and k(𝔭) ⊗R𝔭 S𝔮 is Cohen–Macaulay for all 𝔮 ∈ Spec (S) \ {𝔫} and 𝔭 = 𝔮 ∩ R, and S/𝔭S is catenary and equidimensional for all minimal prime ideals 𝔭 of R. As an application, it is shown that for a k-algebra R and an algebraic field extension K of k, if K ⊗k R is locally equidimensional, then R is a locally filter ring if and only if K ⊗k R is a locally filter ring.
A Necessary and Sufficient Condition for Two Associated Simple Matroids to be Dual
Authors: Mao Hua
Published: February 2014

Let L1 and L2 be finite geometric lattices, and M(L1) and M(L2) be their associated matroids. This paper gives a necessary and sufficient condition for M(L1) and M(L2)* (the dual matroid of M(L2)) to be isomorphic, which is actually an affirmative answer to a question of Welsh.
On Strongly Ordered Congruences and Decompositions of Ordered Semigroups
Authors: Xie Xiang-yun
Published: February 2014

In this paper, we introduce the concept of a strongly ordered congruence on a directed ordered semigroup S. We prove that any strongly ordered congruence on S is a strongly regular congruence. We characterize the finite direct product, subdirect product and full subdirect product of ordered semigroups by using the concepts of strongly ordered congruence and regular congruence on an ordered semigroup S.
A Generalization of Semiregular and Semiperfect Modules
Authors: Özcan A. Çiğdem , Aydoğdu Pınar
Published: February 2014

Let U be a submodule of a module M. We call U a strongly lifting submodule of M if whenever M/U=(A+U)/U ⊕ (B+U)/U, then M=P ⊕ Q such that P ≤ A, (A+U)/U=(P+U)/U and (B+U)/U=(Q+U)/U. This definition is a generalization of strongly lifting ideals defined by Nicholson and Zhou. In this paper, we investigate some properties of strongly lifting submodules and characterize U-semiregular and U-semiperfect modules by using strongly lifting submodules. Results are applied to characterize rings R satisfying that every (projective) left R-module M is τ (M)-semiperfect for some preradicals τ such as Rad , Z2 and δ.
Special Decompositions of Products in Table Algebras
Authors: Arad Zvi , Cohen Efi
Published: February 2014

Table Algebras (A, B) with distinct non-trivial basis elements a, b ∈ B satisfying either [Formula: see text] or [Formula: see text] for some m, n ∈ ℝ+ are studied in this paper. The case [Formula: see text] was partially classified by Arad and Blau, and the case [Formula: see text] was partially classified by Arad and Cohen.
Semilattice Decomposition of Locally Associative AG**-groupoids
Authors: Mushtaq Qaiser , Khan Madad
Published: February 2014

We consider a locally associative AG **-groupoid S and show that it has associative powers. We define ρ on S as aρb if and only if bna = bn+1 and anb = an+1 for all a, b ∈ S, and show that S/ρ is a maximal separative homomorphic image of S. We show that every S can be uniquely expressible as a semilattice Y of locally associative Archimedean AG **-groupoids Sα(α ∈ Y), the semilattice Y is isomorphic to a maximal homomorphic image S/η of S, and Sα(α ∈ Y) are the equivalence classes of S mod η.
Semisimplicity of Locally Finite Graded R#H-Modules
Authors: Guédénon Thomas
Published: February 2014

Let k be a field, Γ an abelian group with a bicharacter, R a colour algebra over k (i.e., a Γ-graded associative k-algebra with identity), H a Hopf colour k-algebra acting on R in such a way that R is a graded H-module algebra and the associated smash product R#H is a colour algebra. The aim of this paper is to study the semisimplicity of the category of H-locally finite Γ-graded R#H-modules. From our main result we deduce that if H is finite-dimensional and R is left graded-noetherian and graded-semisimple, then the colour algebra R#H is graded-semisimple if either H is graded-semisimple or if H is colour-cocommutative and R is colour-commutative and projective in the category of graded R#H-modules.
Generalized Verma Modules over Lie Algebras of Weyl Type
Authors: Xin Bin , Wu Yuezhu
Published: February 2014

For a field 𝔽 of characteristic 0 and an additive subgroup Γ of 𝔽, there corresponds a Lie algebra [Formula: see text] of generalized Weyl type. Given a total order of Γ and a weight Λ, a generalized Verma [Formula: see text]-module M(Λ, ≺) is defined. In this paper, the irreducibility of M(Λ, ≺) is completely determined. It is also proved that an irreducible highest weight module over the [Formula: see text]-infinity algebra [Formula: see text] is quasifinite if and only if it is a proper quotient of a Verma module.
Generalized Dieudonné and Honda Criteria
Authors: Danchev Peter V.
Published: February 2014

Suppose A is an abelian p-group of countable length with a nice subgroup G endowed with a valuation induced by the restricted height valuation of A such that A/G is summable. Then it is proved that A is summable if and only if G is strongly summable in A. This criterion strengthens both the classical Dieudonné and Honda criteria, and also parallels our one argued for σ-summable p-groups of arbitrary lengths. Other analogical criteria of this kind for independent large classes of abelian groups are also established. They extend classical results in this direction.
Lie Quotients for Skew Lie Algebras
Authors: Cabrera Miguel , Sánchez Ortega Juana
Published: February 2014

Let A be a semiprime associative algebra with an involution ∗ over a field of characteristic not 2, let KA be the Lie algebra of all skew elements of A, and let ZKA denote the annihilator of KA. The aim of this paper is to prove that if Q is a ∗-subalgebra of Qs(A) (the Martindale symmetric algebra of quotients of A) containing A, then KQ/ZKQ is a Lie algebra of quotients of KA/ZKA. Similarly, [KQ, KQ]/Z[KQ,KQ] is a Lie algebra of quotients of [KA,KA]/Z[KA,KA].
The Idempotent Quiver of a Nearring
Authors: Peterson Gary L.
Published: February 2014

The idempotent quiver of a nearring R is a directed graph formed using primitive idempotents of R corresponding to the isomorphism classes of the type 2 modules of R. In this paper, we construct such quivers when R satisfies the descending chain condition on right R-subgroups and J2(R) is nilpotent, consider their computation, and study their relationship with the structure of R and its modules.
Extensions of McCoy Rings
Authors: Zhao Renyu , Liu Zhongkui
Published: February 2014

A ring R is called right McCoy if whenever polynomials f(x), g(x) ∈ R[x]∖{0} satisfy f(x)g(x)=0, there exists a nonzero r ∈ R such that f(x)r=0. We continue in this paper the study of right McCoy rings by Nielsen [8]. We first consider properties and basic extensions of right McCoy rings, providing many examples in the process. Next, we show that if R is a right McCoy ring, then R[x] and R[x]/(xn) are right McCoy rings, where (xn) is the ideal generated by xn and n is a positive integer; and that for a right Ore ring R with Q its classical right quotient ring, R is right McCoy if and only if Q is right McCoy.
Two Sufficient Conditions for Vertex-transitive Hamilton Graphs of Prime-power Order
Authors: Zhang Cui , Shi Jiangtao , Shi Wujie
Published: February 2014

A Hamilton cycle in a graph is a cycle going through all vertices of the graph, and a graph is said to be a Hamilton graph if it has a Hamilton cycle. In this article, two sufficient conditions for vertex-transitive Hamilton graphs of prime-power order are given. Using these conditions, two infinite families of Hamilton graphs of order a 2-power are constructed.
Equimultiple Locus of Embedded Algebroid Surfaces and Blowing-up in Arbitrary Characteristic
Authors: Piedra R. , Tornero J. M.
Published: February 2014

This paper describes the behaviour of the equimultiple locus of algebroid surfaces under blowing-up for an arbitrary characteristic ground field, extending previous results of the authors for characteristic zero.
A Note on GP-Injectivity
Authors: Hirano Yasuyuki , Kim Hong Kee , Kim Jin Yong
Published: February 2014

New characteristic properties of left GPGV-rings are given. It is shown that if R is a left GPGV-ring, then for any nonzero element a in R, there is a positive integer n such that an≠ 0 and (RaR+ l(an))⊕ L=R for some left ideal L contained in Soc (RR). As a corollary of this result, we are able to give a positive answer to a question raised by Yue Chi Ming.
Algebra Versus Its Anti-symmetric Algebra
Authors: Choi Seul Hee , Lee Jongwoo , Nam Ki-Bong
Published: February 2014

For a given algebra A= 〈A,+,·〉, we can define its anti-symmetric algebra A-= 〈A-,+,[ , ]〉 using the commutator [ , ] of A, where the sets A and A- are the same. We show that there are isomorphic algebras A1 and A2 such that their anti-symmetric algebras are not isomorphic. We define a special type Lie algebra and show that it is simple.
Minimal Characteristic Algebras for Leftmost k-Normal Identities
Authors: Massé C. , Wang H. , Wismath S. L.
Published: February 2014

A characteristic algebra for a hereditary property of identities is an algebra [Formula: see text] which generates the variety determined by all identities with that property. We use Płonka's construction, and known minimal characteristic algebras for the k-normality and leftmost properties, to construct minimal characteristic algebras of type (2) for leftmost k-normality for 1 ≤ k ≤ 3, and show that Płonka's construction does not always give a minimal algebra.
On Automorphism Groups of Symmetric Cayley Graphs of Finite Simple Groups with Valency Six
Authors: Fang Xingui , Niu Pu , Wang Jie
Published: February 2014

In this paper we investigate the full automorphism groups of six-valent symmetric Cayley graphs Γ = Cay (G,S) for finite non-abelian simple groups G. We prove that for most finite non-abelian simple groups G, if Γ contains no cycle of length 4, then Aut Γ = G · Aut (G,S), where Aut (G,S) ≤ S 6.
On Groups Whose Maximal Cyclic Subgroups Are Maximal
Authors: Juriaans S. O. , Rogério J. R.
Published: February 2014

We consider the problem of classifying those groups whose maximal cyclic subgroups are maximal. We give a complete classification of those groups with this property and which are either soluble or residually finite.
On Some Generalized Identities with Derivations on Multilinear Polynomials
Authors: Carini Luisa , De Filippis Vincenzo , Di Vincenzo Onofrio Mario
Published: February 2014

Let K be a commutative ring with unity, R a prime K-algebra of characteristic different from 2, Z(R) the center of R, f(x1,…,xn) a non-central multilinear polynomial over K, d and δ derivations of R, a and b fixed elements of R. Denote by f(R) the set of all evaluations of the polynomial f(x1,…,xn) in R. If a[d(u),u] + [δ (u),u]b = 0 for any u ∈ f(R), we prove that one of the following holds: (i) d = δ = 0; (ii) d = 0 and b = 0; (iii) δ = 0 and a = 0; (iv) a, b ∈ Z(R) and ad + bδ = 0. We also examine some consequences of this result related to generalized derivations and we prove that if d is a derivation of R and g a generalized derivation of R such that g([d(u),u]) = 0 for any u ∈ f(R), then either g = 0 or d = 0.
The Fischer-Clifford Matrices and Character Table of a Maximal Subgroup of Fi24
Authors: Ali Faryad , Moori Jamshid
Published: February 2014

The Fischer group [Formula: see text] is the largest 3-transposition sporadic group of order 2510411418381323442585600 = 222.316.52.73.11.13.17.23.29. It is generated by a conjugacy class of 306936 transpositions. Wilson [15] completely determined all the maximal 3-local subgroups of Fi24. In the present paper, we determine the Fischer-Clifford matrices and hence compute the character table of the non-split extension 37· (O7(3):2), which is a maximal 3-local subgroup of the automorphism group Fi24 of index 125168046080 using the technique of Fischer-Clifford matrices. Most of the calculations are carried out using the computer algebra systems GAP and MAGMA.
co-∗n-modules
Authors: Yao Lingling , Chen Jianlong
Published: February 2014

It is well known that the notion of ∗-modules plays an important role in the generalization of Morita equivalences. Recently, Wei et al. introduced the concept of ∗n-modules, which induces an equivalence of particular subcategories. In this paper, the dual situation of ∗n-modules, called co -∗n-modules, is considered, and their characterizations and properties are derived. We also present a characterization in terms of category duality, which can be regarded as a generalization of Morita duality. In particular, it is found that the co -selfsmall n-cotilting modules are co -∗n-modules.
Group Properties Characterized by Two-sided Configurations
Authors: Rejali A. , Yousofzadeh A.
Published: February 2014

In this paper, we define a new type of configurations as two-sided configurations, and investigate which group properties can be characterized by them. It is proved that for polycyclic torsion free groups, having the same finite quotient sets does not imply the (two-sided) configuration equivalence. We show that isomorphisms and configuration equivalences coincide for some free products of groups and a class of nilpotent groups.
On Trace Forms on a Class of Commutative Algebras Satisfying an Identity of Degree Four
Authors: Labra Alicia , Rojas-Bruna Carlos
Published: February 2014

In this paper, we deal with commutative algebras A satisfying the identity 2β{(xy)2 - x2y2} + γ{((xy)x)y + ((xy)y)x - (y2x)x - (x2y)y} = 0, where β, γ are scalars. These algebras appeared as one of the four families of degree four identities in Carini, Hentzel and Piacentini-Cattaneo [2]. We prove that if the algebra A admits an identity element, then A is associative. We also prove that there exist trace forms on A. Finally, we prove that if A has a non-degenerate trace form, then A satisfies the identity ((yx)x)x = y((xx)x), a generalization of right alternativity. Our results require characteristic ≠ 2, 3.
Different Prime R-Ideals
Authors: Juglal S. , Groenewald N. J. , Lee K. S. E.
Published: February 2014

It is well known that there are several non-equivalent types of prime near-rings which are all equivalent in the case of associative rings. In this paper we introduce various characterizations of prime modules in a zero-symmetric near-ring R. The connection of a prime R-ideal P of a module M and the ideal (P:M) of the near-ring R is also investigated.
Ω-Gorenstein Projective, Injective and Flat Modules
Authors: Yang Xiaoyan , Liu Zhongkui
Published: February 2014

In this paper, we study some properties of Ω-Gorenstein projective, injective and flat modules and discuss some connections between Ω-Gorenstein injective and Ω-Gorenstein flat modules. We also consider these properties under change of rings.
Rad-injective and Almost-injective Modules and Rings
Authors: Zeyada Nasr A. , Hussein Salah El Din S. , Amin Amr K.
Published: February 2014

We introduce the concepts of almost-injective and rad-injective modules. Basic properties of these modules are given. Using these concepts, we provide some new characterizations of V-rings, semilocal rings and pseudo-Frobenius rings.
Naturally Ordered Transformation Semigroups Preserving an Equivalence Relation and a Cross-section
Authors: Sun Lei , Deng Weina , Pei Huisheng
Published: February 2014

The paper is concerned with the so-called natural order on the semigroup [Formula: see text], where [Formula: see text] is the full transformation semigroup on a set X, E is a non-trivial equivalence on X and R is a cross-section of the partition X/E induced by E. We determine when two elements of TE(X,R) are related under this order, find elements of TE(X,R) which are compatible with ≤ on TE(X,R), and observe the maximal and minimal elements and the covering elements.
Minimal Characteristic Algebras for Rectangular k-Normal Identities
Authors: Hambrook K. , Wismath S. L.
Published: February 2014

A characteristic algebra for a hereditary property of identities of a fixed type τ is an algebra [Formula: see text] such that for any variety V of type τ, we have [Formula: see text] if and only if every identity satisfied by V has the property p. This is equivalent to [Formula: see text] being a generator for the variety determined by all identities of type τ which have property p. Płonka has produced minimal (smallest cardinality) characteristic algebras for a number of hereditary properties, including regularity, normality, uniformity, biregularity, right- and leftmost, outermost, and external-compatibility. In this paper, we use a construction of Płonka to study minimal characteristic algebras for the property of rectangular k-normality. In particular, we construct minimal characteristic algebras of type (2) for k-normality and rectangularity for 1 ≤ k ≤ 3.
Symmetrizable Intersection Matrix Lie Algebras
Authors: Xu Mang , Peng Liangang
Published: February 2014

Associated to every symmetrizable generalized intersection matrix A, we define a Lie algebra, called an SIM-Lie algebra. We prove that SIM-Lie algebras keep unchange under braid-equivalences. Two special cases are considered. In the case when A is a symmetrizable generalized Cartan matrix, we show that the corresponding SIM-Lie algebra is just the Kac–Moody Lie algebra. In another case when A is an intersection matrix, we prove that the corresponding SIM-Lie algebra is just the intersection matrix Lie algebra in the sense of Slodowy.
Co-Cohen-Macaulay Modules and Generalized Local Cohomology
Authors: Mafi Amir
Published: February 2014

Let (R,𝔪) be a Noetherian local ring, 𝔞 a proper ideal of R, and M, N two finitely generated R-modules of finite projective dimension m and of finite dimension n, respectively. It is shown that if n ≤ 2, then the generalized local cohomology module [Formula: see text] is a co-Cohen-Macaulay module. Additionally, we show that [Formula: see text] for all i > m+s and [Formula: see text], where s is the cohomological dimension of N with respect to 𝔞.
Minimal Degree of Faithful Quasi-permutation Representations of p-Groups
Authors: Behravesh Houshang , Ghaffarzadeh Ghodrat
Published: February 2014

In [2], we gave algorithms to calculate c(G), q(G) and p(G) for a finite group G. In this paper, we show that for a finite p-group G, where p is a prime, q(G)=p(G). Moreover, for odd prime p, c(G)=q(G)=p(G).
Actions of Generalized Derivations on Multilinear Polynomials in Prime Rings
Authors: Argaç Nurcan , De Filippis Vincenzo
Published: February 2014

Let K be a commutative ring with unity, R a non-commutative prime K-algebra with center Z(R), U the Utumi quotient ring of R, C=Z(U) the extended centroid of R, I a non-zero two-sided ideal of R, H and G non-zero generalized derivations of R. Suppose that f(x1,…,xn) is a non-central multilinear polynomial over K such that H(f(X))f(X)-f(X)G(f(X))=0 for all X=(x1,…,xn)∈ In. Then one of the following holds: (1) There exists a ∈ U such that H(x)=xa and G(x)=ax for all x ∈ R. (2) f(x1,…,xn)2 is central valued on R and there exist a, b ∈ U such that H(x)=ax+xb and G(x)=bx+xa for all x ∈ R. (3) char (R)=2 and R satisfies s4, the standard identity of degree 4.
On the Prime Spectrum of an Integral Domain with Finite Spectral Semistar Operations
Authors: Mimouni A.
Published: February 2014

In this paper, we investigate the prime spectrum of an integral domain R with a finite number of spectral semistar operations. This will be done by seeking for a possible link between the cardinality of the set SpSS (R) of all spectral semistar operations on R and its Krull dimension. In particular, we prove that if | SpSS (R)|=n+ dim R, then 2| Max (R)|≤ n+1. This leads us to give a complete description for the spectrum of a domain R such that | SpSS (R)|=n+ dim R for 1 ≤ n ≤ 5.
On Invariants of Some Maximal Subgroups of Finite Classical Groups
Authors: Nan Jizhu , Qin Yufang
Published: February 2014

The maximal subgroups of the finite classical groups are divided into nine classes by Aschbacher's theorem. In this paper, we give explicit transcendental bases of the invariant subfields of those maximal subgroups of classical groups of linear, symplectic and unitary cases that lie in the first two of these classes. Also, we show that the invariant rings of the maximal subgroups of the finite linear groups that lie in the first class are polynomial rings.
On Weights and Intersections of p-Subgroups
Authors: Wang Baoshan , Wang Lizhong
Published: February 2014

Let B be a p-block of a finite group G over F and (Q, S) a weight of B. In this paper, we show that Q must be an intersection of two Sylow p-subgroups of G and Q must also be contained in the intersection of two defect groups of B.
G-Gorenstein Modules
Authors: Aghajani Mohsen , Zakeri Hossein
Published: February 2014

Let R be a commutative Noetherian ring. In this paper, we study those finitely generated R-modules whose Cousin complexes provide Gorenstein injective resolutions. We call such a module a G-Gorenstein module. Characterizations of G-Gorenstein modules are given and a class of such modules is determined. It is shown that the class of G-Gorenstein modules strictly contains the class of Gorenstein modules. Also, we provide a Gorenstein injective resolution for a balanced big Cohen-Macaulay R-module. Finally, using the notion of a G-Gorenstein module, we obtain characterizations of Gorenstein and regular local rings.
OD-Characterization of the Projective Special Linear Groups L2(q)
Authors: Zhang Liangcai , Shi Wujie
Published: February 2014

Let L2(q) be the projective special linear group, where q is a prime power. In the present paper, we prove that L2(q) is OD-characterizable by using the classification of finite simple groups. A new method is introduced in order to deal with the subtle changes of the prime graph of a group in the discussion of its OD-characterization. This not only generalizes a result of Moghaddamfar, Zokayi and Darafsheh, but also gives a positive answer to a conjecture put forward by Shi.
Cleanness of the Group Ring of an Abelian p-Group over a Commutative Ring
Authors: Wang Xiulan , You Hong
Published: February 2014

A ring R is called clean if every element is the sum of an idempotent and a unit, while R is called uniquely clean if this representation is unique. In this article, we prove that if R is a commutative ring and G is an abelian p-group with p in J(R), then RG is clean if and only if R is clean. Moreover, when G is a locally finite group, some conditions for RG to be uniquely clean are given.
The Square Mapping Graphs of Finite Commutative Rings
Authors: Wei Yangjiang , Tang Gaohua , Su Huadong
Published: February 2014

For a finite commutative ring R, the square mapping graph of R is a directed graph Γ(R) whose set of vertices is all the elements of R and for which there is a directed edge from a to b if and only if a2=b. We establish necessary and sufficient conditions for the existence of isolated fixed points, and the cycles with length greater than 1 in Γ(R). We also examine when the induced subgraph on the set of zero-divisors of a local ring with odd characteristic is semiregular. Moreover, we completely determine the finite commutative rings whose square mapping graphs have exactly two, three or four components.
Rad-⊕-Supplemented Modules and Cofinitely Rad-⊕-Supplemented Modules
Authors: Ecevit Şule , Koşan Muhammet T. , Tribak Rachid
Published: February 2014

A module M is called (cofinitely) Rad-⊕-supplemented if every (cofinite) submodule of M has a Rad-supplement that is a direct summand of M. We prove that if M is a coatomic cofinitely Rad-⊕-supplemented module, then M is an irredundant sum of local direct summands. We show that the classes of cofinitely Rad-⊕-supplemented modules and Rad-⊕-supplemented modules are closed under finite direct sums. We also show that every direct summand of a weak duo (cofinitely) Rad-⊕-supplemented module is (cofinitely) Rad-⊕-supplemented.
On Weakly Laskerian and Weakly Cofinite Modules
Authors: Khashyarmanesh Kazem , Koşan M. Tamer , Şahinkaya Serap
Published: February 2014

Let R be a commutative Noetherian ring with non-zero identity, 𝔞 an ideal of R and M a finitely generated R-module. We assume that N is a weakly Laskerian R-module and r is a non-negative integer such that the generalized local cohomology module [Formula: see text] is weakly Laskerian for all i < r. Then we prove that [Formula: see text] is also weakly Laskerian and so [Formula: see text] is finite. Moreover, we show that if s is a non-negative integer such that [Formula: see text] is weakly Laskerian for all i, j ≥ 0 with i ≤ s, then [Formula: see text] is weakly Laskerian for all i ≤ s and j ≥ 0. Also, over a Gorenstein local ring R of finite Krull dimension, we study the question when the socle of [Formula: see text] is weakly Laskerian?
A Class of Trinomials with Galois Group Sn
Authors: Bishnoi Anuj , Khanduja Sudesh K.
Published: February 2014

A well known result of Schur states that if n is a positive integer and a0, a1,…,an are arbitrary integers with a0an coprime to n!, then the polynomial [Formula: see text] is irreducible over the field ℚ of rational numbers. In case each ai = 1, it is known that the Galois group of fn(x) over ℚ contains An, the alternating group on n letters. In this paper, we extend this result to a larger class of polynomials fn(x) which leads to the construction of trinomials of degree n for each n with Galois group Sn, the symmetric group on n letters.
Groups with Finiteness Conditions on Commutators
Authors: De Falco Maria , de Giovanni Francesco , Musella Carmela
Published: February 2014

The structure of groups for which certain sets of commutator subgroups are finite is investigated. In particular, the relation between such groups and groups with finite conjugacy classes of elements is discussed.
Weight Parameterization of Simple Modules for p-Solvable Groups
Authors: Puig Lluis
Published: February 2014

The weights for a finite group G with respect to a prime number p were introduced by Jon Alperin, in order to formulate his celebrated conjecture affirming that the number of G-conjugacy classes of weights of G coincides with the number of isomorphism classes of simple kG-modules, where k is an algebraically closed field of characteristic p. Thirty years ago, Tetsuro Okuyama already proved that in the class of p-solvable groups this conjecture holds. In this paper, for the p-solvable groups, on the one hand we exhibit a natural bijection — namely compatible with the action of the group of outer automorphisms of G — between the sets of isomorphism classes of simple kG-modules M and of G-conjugacy classes of weights (R,Y), up to the choice of a polarization. On the other hand, we determine the relationship between a multiplicity module of M and Y. In an Appendix, we show that the bijection defined by Gabriel Navarro for the groups of odd order coincides with our bijection for a particular choice of the polarization.
Automorphisms of Subconstituents of Symplectic Graphs
Authors: Gu Zhenhua , Wan Zhexian
Published: February 2014

In this paper, the full automorphism groups of the two subconstituents of symplectic graphs over finite fields are determined.
Locally Maximal Idempotent-generated Subsemigroups of Finite Orientation-preserving Singular Partial Transformation Semigroups
Authors: Zhao Ping , Yang Mei
Published: February 2014

In this paper we describe locally maximal idempotent-generated subsemigroups of finite orientation-preserving singular partial transformation semigroups SPOPn and obtain a complete classification. We also obtain a classification of locally maximal idempotent-generated subsemigroups of finite order-preserving singular partial transformation semigroups [Formula: see text] with respect to ≤k.
The Global Dimension of the Endomorphism Algebra of a Generator-cogenerator for a Subcategory
Authors: Guo Jingjing
Published: February 2014

Let A be a hereditary Artin algebra and T a tilting A-module. The possibilities for the global dimension of the endomorphism algebra of a generator-cogenerator for the subcategory T⊥ in A-mod are determined in terms of relative Auslander-Reiten orbits of indecomposable A-modules in T⊥.
Krull Modules
Authors: Kim Hwankoo , Kim Myeong Og
Published: February 2014

In this article, we generalize the concepts of several classes of domains (which are related to Krull domains) to torsion-free modules, and show that for a faithful multiplication module M over an integral domain R, M is a Krull module if and only if R is a Krull domain. Then we characterize Krull, Dedekind, and factorial modules.
Endomorphisms Preserving Coordinates of Polynomial Algebras
Authors: Li Yu-Chang , Yu Jie-Tai
Published: February 2014

It is proved that the Jacobian of a k-endomorphism of k[x1,…,xn] over a field k of characteristic zero, taking every tame coordinate to a coordinate, must be a nonzero constant in k. It is also proved that the Jacobian of an R-endomorphism of A=:R[x1,…,xn] (where R is a polynomial ring in a finite number of variables over an infinite field k), taking every R-linear coordinate of A to an R-coordinate of A, is a nonzero constant in k.
Finite Nilpotent Groups Having Exactly Four Conjugacy Classes of Non-normal Subgroups
Authors: Gong Lü , Cao Hongping , Chen Guiyun
Published: February 2014

Finite nilpotent groups having exactly four conjugacy classes of non-normal subgroups are classified.
Non-Artinian Local Cohomology with Respect to a Pair of Ideals
Authors: Tehranian Abolfazl , Pour Eshmanan Talemi Atiyeh
Published: February 2014

Let R be a commutative Noetherian ring, I, J two ideals of R, and M an R-module. For a non-negative integer t, we show: (a) If [Formula: see text] for all j < t and [Formula: see text] are finite (resp., Artinian), then [Formula: see text] is finite (resp., Artinian). (b) If [Formula: see text] for all j < t and [Formula: see text] are finite (resp., Artinian), then [Formula: see text] is finite (resp., Artinian). In addition, if (R,𝔪) is a local ring, J a non-nilpotent ideal, and M a finite R-module, then we show that [Formula: see text] is not Artinian for some i ∈ ℕ0.
Certain Additive Maps on (m+n+1)-Power Closed Lie Ideals
Authors: Liu Kun-Shan
Published: February 2014

Let R be a prime ring and m, n be fixed non-negative integers such that m+n ≠ 0. Suppose L is an (m+n+1)-power closed Lie ideal, and this means um+n+1∈ L for all u ∈ L. If char R=0 or a prime p > 2(m+n), we characterize the additive maps d: L → R satisfying d(um+n+1)=(m+n+1)umd(u)un (resp., d(um+n+1)=umd(u)un) for all u ∈ L.
Lie Invariants in Two and Three Variables
Authors: Bremner Murray R. , Hu Jiaxiong
Published: February 2014

We use computer algebra to determine the Lie invariants of degree ≤ 12 in the free Lie algebra on two generators corresponding to the natural representation of the simple 3-dimensional Lie algebra 𝔰𝔩2(ℂ). We then consider the free Lie algebra on three generators, and compute the Lie invariants of degree ≤ 7 corresponding to the adjoint representation of 𝔰𝔩2(ℂ), and the Lie invariants of degree ≤ 9 corresponding to the natural representation of 𝔰𝔩3(ℂ). We represent the action of 𝔰𝔩2(ℂ) and 𝔰𝔩3(ℂ) on Lie polynomials by computing the coefficient matrix with respect to the basis of Hall words.
L-R-Smash Products and L-R-Twisted Tensor Products of Algebras
Authors: Ciungu Mădălin , Panaite Florin
Published: February 2014

We introduce a common generalization of the L-R-smash product and twisted tensor product of algebras, under the name L-R-twisted tensor product of algebras. We investigate some properties of this new construction, for instance, we prove a result of the type “invariance under twisting” and we show that under certain circumstances L-R-twisted tensor products of algebras may be iterated.
A Note on Comultiplication Modules
Authors: Wang Yongduo , Liu Yang
Published: February 2014

Let R be a commutative ring with identity. An R-module M is said to be a comultiplication module if for every submodule N of M, there exists an ideal I of R such that N=(0:M I). In this paper, we show: (1) If M is a comultiplication module and N is a copure submodule of M, then M/N is a comultiplication module. (2) If M is a comultiplication module satisfying the DAC and N ≤ M, then N ≤e M if and only if there exists I ≪ R such that N=(0:M I). (3) If M is a comultiplication module satisfying the DAC, then M is finitely cogenerated. Finally, we give a partial answer to a question posed by Ansari-Toroghy and Farshadifar.
Process-variation-aware mapping of best-effort and real-time streaming applications to MPSoCs
Authors: Mirzoyan Davit , Akesson Benny , Goossens Kees
Published: February 2014

As technology scales, the impact of process variation on the maximum supported frequency (FMAX) of individual cores in a multiprocessor system-on-chip (MPSoC) becomes more pronounced. Task allocation without variation-aware performance analysis can greatly compromise performance and lead to a significant loss in
yield
, defined as the percentage of manufactured chips satisfying the
application timing requirement
. We propose variation-aware task allocation for best-effort and real-time streaming applications modeled as task graphs. Our solutions are primarily based on the throughput requirement, which is the most important timing requirement in many real-time streaming applications.

The four main contributions of this work are (1) distinguishing best-effort firm real-time and soft real-time application classes, which require different optimization criteria, (2) using dataflow graphs, which are well suited for modeling and analysis of streaming applications, we explicitly model task execution both in terms of clock cycles (which is independent of variation) and seconds (which does depend on the variation of the resource), which we connect by an explicit binding, (3) we present two optimization approaches, which give different improvement results at different costs, (4) we present both exhaustive and heuristic algorithms that implement the optimization approaches. Our variation-aware mapping algorithms are tested on models of seven real applications and are compared to mapping methods that are unaware of hardware variation. Our results demonstrate (1) improvements in the average performance (3% on average) for best-effort applications, and (2) for firm real-time and soft real-time applications, yield improvements of up to 27% with an average of 15%, showing the effectiveness of our approaches.
Contention-free executions for real-time multiprocessor scheduling
Authors: Lee Jinkyu , Easwaran Arvind , Shin Insik
Published: February 2014

A time slot is defined as
contention-free
if the number of jobs with remaining executions in the slot is no larger than the number of processors, or
contending
, otherwise. Then an important property holds that in any contention-free slot, all jobs with remaining executions are guaranteed to be scheduled as long as the scheduler is work-conserving. This article aims at improving schedulability by utilizing the contention-free slots. To achieve this, this article presents a policy (called CF policy) that moves some job executions from contending slots to contention-free ones. This policy can be employed by any work-conserving, preemptive scheduling algorithm, and we show that any algorithm extended with this policy dominates the original algorithm in terms of schedulability. We also present improved schedulability tests for algorithms that employ this policy, based on the observation that interference from jobs is reduced when their executions are postponed to contention-free slots. Simulation results demonstrate that the CF policy, incorporated into existing algorithms, significantly improves schedulability of those existing algorithms.
Hybrid compilation and optimization for java-based digital TV platforms
Authors: Jung Dong-Heon , Moon Soo-Mook , Oh Hyeong-Seok
Published: February 2014

The Java-based software platform for interactive digital TV (DTV) is composed of the system/middleware class statically installed on the DTV set-top box and the
xlet
applications dynamically downloaded from the TV stations. The xlet application includes Java classes and image/text files. The xlets are executed only when the TV viewer initiates an interaction, even if the xlets have been completely downloaded. To achieve high performance on this dual-component, user-initiated system, existing just-in-time (JIT) compilation and optimization is not enough; instead, ahead-of-time and idle-time compilation and optimization are also needed, requiring a hybrid compilation and optimization environment. We constructed such a hybrid environment for a commercial DTV software platform and evaluated it using real, on-air xlet applications. Our experimental results show that the proposed hybrid environment can improve the DTV Java performance by more than three times, compared to the JIT-only environment, with little change to other DTV behavior.
Indexing for summary queries
Authors: Yi Ke , Wang Lu , Wei Zhewei
Published: February 2014

Database queries can be broadly classified into two categories: reporting queries and aggregation queries. The former retrieves a collection of records from the database that match the query's conditions, while the latter returns an aggregate, such as count, sum, average, or max (min), of a particular attribute of these records. Aggregation queries are especially useful in business intelligence and data analysis applications where users are interested not in the actual records, but some statistics of them. They can also be executed much more efficiently than reporting queries, by embedding properly precomputed aggregates into an index.

However, reporting and aggregation queries provide only two extremes for exploring the data. Data analysts often need more insight into the data distribution than what those simple aggregates provide, and yet certainly do not want the sheer volume of data returned by reporting queries. In this article, we design indexing techniques that allow for extracting a statistical summary of all the records in the query. The summaries we support include frequent items, quantiles, and various sketches, all of which are of central importance in massive data analysis. Our indexes require linear space and extract a summary with the optimal or near-optimal query cost. We illustrate the efficiency and usefulness of our designs through extensive experiments and a system demonstration.
Pufferfish
Authors: Kifer Daniel , Machanavajjhala Ashwin
Published: February 2014

In this article, we introduce a new and general privacy framework called Pufferfish. The Pufferfish framework can be used to create new privacy definitions that are customized to the needs of a given application. The goal of Pufferfish is to allow experts in an application domain, who frequently do not have expertise in privacy, to develop rigorous privacy definitions for their data sharing needs. In addition to this, the Pufferfish framework can also be used to study existing privacy definitions.

We illustrate the benefits with several applications of this privacy framework: we use it to analyze differential privacy and formalize a connection to attackers who believe that the data records are independent; we use it to create a privacy definition called hedging privacy, which can be used to rule out attackers whose prior beliefs are inconsistent with the data; we use the framework to define and study the notion of composition in a broader context than before; we show how to apply the framework to protect unbounded continuous attributes and aggregate information; and we show how to use the framework to rigorously account for prior data releases.
Coupled structure-from-motion and 3D symmetry detection for urban facades
Authors: Ceylan Duygu , Mitra Niloy J. , Zheng Youyi , Pauly Mark
Published: February 2014

Repeated structures are ubiquitous in urban facades. Such repetitions lead to ambiguity in establishing correspondences across sets of unordered images. A decoupled structure-from-motion reconstruction followed by symmetry detection often produces errors: outputs are either noisy and incomplete, or even worse, appear to be valid but actually have a wrong number of repeated elements. We present an optimization framework for extracting repeated elements in images of urban facades, while simultaneously calibrating the input images and recovering the 3D scene geometry using a graph-based global analysis. We evaluate the robustness of the proposed scheme on a range of challenging examples containing widespread repetitions and nondistinctive features. These image sets are common but cannot be handled well with state-of-the-art methods. We show that the recovered symmetry information along with the 3D geometry enables a range of novel image editing operations that maintain consistency across the images.
k
-d Darts
Authors: Ebeida Mohamed S. , Patney Anjul , Mitchell Scott A. , Dalbey Keith R. , Davidson Andrew A. , Owens John D.
Published: February 2014

We formalize sampling a function using
k
-d darts. A
k
-d Dart is a set of independent, mutually orthogonal,
k
-dimensional hyperplanes called
k
-d flats. A dart has
d
choose
k
flats, aligned with the coordinate axes for efficiency. We show
k
-d darts are useful for exploring a function's properties, such as estimating its integral, or finding an exemplar above a threshold. We describe a recipe for converting some algorithms from point sampling to
k
-d dart sampling, if the function can be evaluated along a
k
-d flat.

We demonstrate that
k
-d darts are more efficient than point-wise samples in high dimensions, depending on the characteristics of the domain: for example, the subregion of interest has small volume and evaluating the function along a flat is not too expensive. We present three concrete applications using line darts (1-d darts): relaxed maximal Poisson-disk sampling, high-quality rasterization of depth-of-field blur, and estimation of the probability of failure from a response surface for uncertainty quantification. Line darts achieve the same output fidelity as point sampling in less time. For Poisson-disk sampling, we use less memory, enabling the generation of larger point distributions in higher dimensions. Higher-dimensional darts provide greater accuracy for a particular volume estimation problem.
Strong simulation
Authors: Ma Shuai , Cao Yang , Fan Wenfei , Huai Jinpeng , Wo Tianyu
Published: February 2014

Graph pattern matching is finding all matches in a data graph for a given pattern graph and is often defined in terms of subgraph isomorphism, an
NP
-complete problem. To lower its complexity, various extensions of graph simulation have been considered instead. These extensions allow graph pattern matching to be conducted in cubic time. However, they fall short of capturing the topology of data graphs, that is, graphs may have a structure drastically different from pattern graphs they match, and the matches found are often too large to understand and analyze. To rectify these problems, this article proposes a notion of
strong simulation
, a revision of graph simulation for graph pattern matching. (1) We identify a set of criteria for preserving the topology of graphs matched. We show that strong simulation preserves the topology of data graphs and finds a bounded number of matches. (2) We show that strong simulation retains the same complexity as earlier extensions of graph simulation by providing a cubic-time algorithm for computing strong simulation. (3) We present the locality property of strong simulation which allows us to develop an effective distributed algorithm to conduct graph pattern matching on distributed graphs. (4) We experimentally verify the effectiveness and efficiency of these algorithms using both real-life and synthetic data.
Linear-Time Approximation for Maximum Weight Matching
Authors: Duan Ran , Pettie Seth
Published: February 2014

The
maximum cardinality
and
maximum weight matching
problems can be solved in
Õ
(
m
√
n
) time, a bound that has resisted improvement despite decades of research. (Here
m
and
n
are the number of edges and vertices.) In this article, we demonstrate that this “
m
√
n
barrier” can be bypassed by approximation. For any
ε
> 0, we give an algorithm that computes a (1 −
ε
)-approximate maximum weight matching in
O
(
mε
−1
log
ε
−1
) time, that is, optimal
linear time
for any fixed
ε
. Our algorithm is dramatically simpler than the best exact maximum weight matching algorithms on general graphs and should be appealing in all applications that can tolerate a negligible relative error.
Context-based coherent surface completion
Authors: Harary Gur , Tal Ayellet , Grinspun Eitan
Published: February 2014

We introduce an algorithm to synthesize missing geometry for a given triangle mesh that has “holes.” Similarly to previous work, the algorithm is context based in that it fills the hole by synthesizing geometry that is similar to the remainder of the input mesh. Our algorithm goes further to impose a coherence objective. A synthesis is coherent if every local neighborhood of the filled hole is similar to some local neighborhood of the input mesh. This requirement avoids undesired features such as can occur in context-based completion. We demonstrate the algorithm's ability to fill holes that were difficult or impossible to fill in a compelling manner by earlier approaches.
A practical algorithm for rendering interreflections with all-frequency BRDFs
Authors: Xu Kun , Cao Yan-Pei , Ma Li-Qian , Dong Zhao , Wang Rui , Hu Shi-Min
Published: February 2014

Algorithms for rendering interreflection (or indirect illumination) effects often make assumptions about the frequency range of the materials' reflectance properties. For example, methods based on Virtual Point Lights (VPLs) perform well for diffuse and semi-glossy materials but not so for highly glossy or specular materials; the situation is reversed for methods based on ray tracing. In this article, we present a practical algorithm for rendering interreflection effects with all-frequency BRDFs. Our method builds upon a spherical Gaussian representation of the BRDF, based on which a novel mathematical development of the interreflection equation is made. This allows us to efficiently compute one-bounce interreflection from a triangle to a shading point, by using an analytic formula combined with a piecewise linear approximation. We show through evaluation that this method is accurate for a wide range of BRDFs. We further introduce a hierarchical integration method to handle complex scenes (i.e., many triangles) with bounded errors. Finally, we have implemented the present algorithm on the GPU, achieving rendering performance ranging from near interactive to a few seconds per frame for various scenes with different complexity.