bluuebunny/crossref_metadata_2025_split huggingface dataset:
On some properties of group rings
Authors: Karpilovsky G. 
Published: April 2009

AbstractLet Out (RG) be the set of all outer R-automorphisms of a group ring RG of arbitrary group G over a commutative ring R with 1. It is proved that there is a bijective correspondence between the set Out (RG) and a set consisting of R(G × G)-isomorphism classes of R-free R(G × G)-modules of a certain type. For the case when G is finite and R is the ring of algebraic integers of an algebraic number field the above result implies that there are only finitely many conjugacy classes of group bases in RG. A generalization of a result due to R. Sandling is also provided.
A fixed point theorem for non-expansive, condensing mappings
Authors: Chandler Eric , Faulkner Gary 
Published: April 2009

AbstractA lemma is obtained which guarantees that non-expansive mappings on contractive spaces have fixed points. An example shows that Schauders's fixed point theorem cannot be extended to contractive spaces, but a theorem for contractive spaces, analogous to a result of B. N. Sadovskii on convex spaces, is derived from the lemma. Finally, some local results for ε-chainable contractive spaces are given.
Bhaskar Rao designs from cyclotomy
Authors: Street Deborah J. 
Published: April 2009

AbstractA Bhaskar Rao design is obtained from the incidence matrix of a partially balanced incomplete block design with m associate classes by negating some elements of the matrix in such a way that the inner product of rows α and β is ci if α and β are ith associates. In this paper we use nested designs constructed from unions of cyclotomic classes to give Bhaskar Rao designs.
On a method for constructing Bergman kernels
Authors: Azzam A. , Kreyszig E. 
Published: April 2009

AbstractWe establish a method of constructing kernels of Bergman operators for second-order linear partial differential equations in two independent variables, and use the method for obtaining a new class of Bergman kernels, which we call modified class E kernels since they include certain class E kernals. They also include other kernels which are suitable for global representations of solutions (whereas Bergman operators generally yield only local representations).
Transposable and symmetrizable matrices
Authors: McCarthy David , McKay Brendan D. 
Published: April 2009

AbstractA square matrix A is transposable if P(RA) = (RA)T for some permutation matrices p and R, and symmetrizable if (SA)T = SA for some permutation matrix S. In this paper we find necessary and sufficient conditions on a permutation matrix P so that A is always symmetrizable if P(RA) = (RA)T for some permutation matrix R.
Pair-packings and projective planes
Authors: Stinson D. R. 
Published: April 2009

AbstractAn (n + 1, n2 + n + 1)-packing is a collection of blocks, each of size n + 1, chosen from a set of size n2 + n + 1, such that no pair of points is contained in more than one block. If any two blocks contain a common point, then the packing can be extended to a projective plane of order n, provided the number of blocks is sufficiently large. We study packings which have a pair of disjoint blocks (such a packing clearly cannot be extended to a projective plane of order n). No such packing can contain more than n2 + n/2 blocks. Also, if n is the order of a projective plane, then we can construct such a packing with n2 + 1 blocks.
Critical associated metrics on contact manifolds
Authors: Blair David E. 
Published: April 2009

AbstractDefining a function on the set of all Riemannian metrics associated to a contact form on a compact manifold by taking the integral of the Ricci curvature in the direction of the characteristic vector field, it is shown that on a compact regular contact manifold the only critical points of this function are the metrics for which the characteristic vector field generates a group of isometrics.
Calculus in f-algebras
Authors: Beukers F. , Huijsmans C. B. 
Published: April 2009

AbstractLet A be an Archimedean, uniformly complete, semiprime f-algebra and F(X1,…Xn) ∈ R+ [X1,…Xn] a homogeneous polynomial of degree p (p∈ N). It is shown that (F(u 1…unn))1/p exists in A+ for all u1…un ∈ A+.
Jakubowski starlike integral operators
Authors: Kumar Vinod , Shukla S. L. 
Published: April 2009

AbstractLet S(m, M) be the set of functions regular and satisfying │zf′(z)/f(z) – m│< M in │z│ <1, where│m –│ <M;≦ m; and let S*(p) be the set of starlike functions of order p, 0≦ p <1. In this paper we obtain integral operators which map S(m, M) into S(mM) and S* (p) × S(mM) into S*(p). Our results improve and generalize many recent results.
Two further Ramanujan pairs
Authors: Hirschhorn Michael D. 
Published: April 2009

AbstractIn a recent article, George E. Andrews considers a generalization of the Rogers-Ramanujan identities involving a pair of infinite sequences of positive integers, which he calls a Ramanujan pair. He lists the known Ramanujan pairs and conjectures that there are no more. The object of this note is to establish the existence of two further Ramanujan pairs.
On the law of the iterated logarithm in the infinite variance case
Authors: Maller R. A. 
Published: April 2009

AbstractThe main purpose of the paper is to give necessary and sufficient conditions for the almost sure boundedness of (Sn – αn)/B(n), where Sn = X1 + X2 + … + XmXi being independent and identically distributed random variables, and αnand B(n) being centering and norming constants. The conditions take the form of the convergence or divergence of a series of a geometric subsequence of the sequence P(Sn − αn > a B(n)), where a is a constant. The theorem is distinguished from previous similar results by the comparative weakness of the subsidiary conditions and the simplicity of the calculations. As an application, a law of the iterated logarithm general enough to include a result of Feller is derived.
Nonexistence of an extremal graph of a certain type
Authors: Stanton R. G. , Seach S. T. E. , Cowan D. D. 
Published: April 2009

AbstractCubic Moore graphs of diameter k on 3.2k−2 vertices do not exist for k > 2. This paper exhibits the first known case of nonexistence for generalized cubic Moore graphs when the number of vertices is just less than the critical number for a Moore graph: the generalized Moore graph on 44 vertices does not exist.
A generalization of the Hall semigroup of a band
Authors: Szendrei Mária B. 
Published: April 2009

AbstractLet E be a band and ε a compatible partition on it. If S is an orthodox semigroup with band of idempotents E such that there exists a congruence on S inducing the partition ε then we define a homomorphism of S into a Hall semigroup whose kernel is the greatest congruence on S inducing the partition ε. On the other hand, we define a subsemigroup of the Hall semigroup WE possessing the property that S is an othodox semigroup with band of idempotents E which has a congruence inducing ε if and only if the range of the Hall homomoprhism of S into WE is contained in .
Some cancellation theorems
Authors: Shastri A. R. 
Published: April 2009

AbstractIf G, H and B are groups such that G × B ≃ H × B, G/[G, G]. Z(G) is free abelian and B is finitely generated abelian, then G ≃ H. The equivalence classes of triples (Vξ,A) where Vand A are finitely generated free abelian groups and ξ: V⊗ V → A is a bilinear form constitute a semigroup B undera natural external orthogonal sum. This semigroup B is cancellative. A cancellation theorem for class 2 nilpotent groups is deduced.
Some remarks on a One-dimensional skip-free process with repulsion
Authors: Pakes Anthony G. 
Published: April 2009

AbstractWe extend the results obtained by Hines and Thompson for a Markov chain which has a single reflecting barrier at the origin, nearest neighbour transitions and which moves from {j} to {j + l} with probability j/(j + 1). Martingale limit theorems are used to work out an asymptotic theory for a general class of such chains for which the probability above has the form l – λ(j) = O>λ(j)>1 (j ∈N),λ(j)→ O (j →∞)and Σλ(j)=∞ We discuss the case where the last sum is finite and some alternative versions of the general case.
Fixed points of certain involutions in Banach spaces
Authors: Khan M. S. , Imdad M. 
Published: April 2009

AbstractSome results on fixed points of certain involutions in Banach spaces have been obtained, and whence a few coincidence theorems are also derived. These are indeed generalization of previously known results due to Browder, Goebel-Zlotkiewicz and Iséki. Illustrative examples are also given.
Extension and inversion of extended orthomorphisms on Riesz spaces
Authors: Duhoux Michel , Meyer Mathieu 
Published: April 2009

AbstractLet E be an Archimedean Riesz space and let Orth∞(E) be the f-algebra consisting of all extended orthomorphisms on E, that is, of all order bounded linear operators T:D→E, with D an order dense ideal in E, such that T(B∩D) ⊆ B for every band B in E. We give conditions on E and on a Riesz subspace F of E insuring that every T ∈ Orth∞(F) can be extended to some ∈ Orth∞(E), and we also consider the problem of inversing an extended orthomorphism on its support. The same problems are also studied in the case of σ-orthomorphisms, that is, extended orthomorphisms with a super order dense domain. Furthermore, some applications are given.
Invex functions and duality
Authors: Craven B. D. , Glover B. M. 
Published: April 2009

AbstractFor both differentiable and nondifferentiable functions defined in abstract spaces we characterize the generalized convex property, here called cone-invexity, in terms of Lagrange multipliers. Several classes of such functions are given. In addition an extended Kuhn-Tucker type optimality condition and a duality result are obtained for quasidifferentiable programming problems.
Continuous programming containing arbitrary norms
Authors: Chandra S. , Craven B. D. , Husain I. 
Published: April 2009

AbstractOptimality conditions and duality results are obtained for a class of cone constrained continuous programming problems having terms with arbitrary norms in the objective and constraint functions. The proofs are based on a Fritz John theorem for constrained optimization in abstract spaces. Duality results for a fractional analogue of such continuous programming problems are indicated and a nondifferentiable mathematical programming duality result, not explicitly reported in the literature, is deduced as a special case.
Measures coniques sur un espace de Banach ou son dual
Authors: Becker Richard 
Published: April 2009

AbstractSi E et F sont deux espaces vectoriels en dualité séparante, M+(E, F) désigne le cône des mesures coniques positives sur E mis en dualité avec F, c'est à dire le cônes des formes postives sur le treillis de fonctions sur E engendré par F. Ce sont des objets plus généraux que les mesures cylindriques admettant des moments finis d'ordre un.On part d'abord d'une mesure conique représentée par une mesure de Radon sur le complété faible de E et on donne des critéres (par exemple R.N.P.) pour qu'elle le soit sur l'espace E lui-même.On étudie ensuite les cônes faiblement complets saillants (classe L) contenus dans un espace de Banach ou dans le dual d'un espace de Fréchet F; on montre notamment qu' un cône faiblement fermé contenu dans F′ est dans Lsi son polaire dans F est positivement engendré.Si B est un espace de Banach et 11 ⊄ B, on cherche à prologner une μ ∈ M+(B′, B) en un élement de M+ (B′, B″). On montre également que, si X est un convexe compact, toute fonction vérifiant le calcul barycentrique sur X est continue sur des ensembles fixes que l'on précise.Enfin on donne des conditions (de type bornologique) sur un e.l.c.s E, permettant d'interpréter une μ ∈ M+ (E, E′) comme une mesure conique sur un espace normé.
Multipliers of Banach valued function spaces
Authors: Lai Hang-Chin 
Published: April 2009

AbstractLet A be a commutative Banach algebra with identity of norm 1, X a Banach A-module and G a locally compact abeian group with Haar measure. Then the multipliers from an A -valued function algebra into an X-valued function space is studied. We characterize the multiplier spaces as the following isometrically isomorphic relations under some appropriate conditions:
Triangles in a complete chromatic graph
Authors: Goodman A. W. 
Published: April 2009

AbstractSuppose that in a complete graph on N points, each edge is given arbitrarily either the color red or the color blue, but the total number of blue edges is fixed at T. We find the minimum number of monochromatic triangles in the graph as a function of N and T. The maximum number of monochromatic triangles presents a more difficult problem. Here we propose a reasonable conjecture supported by examples.
Automorphisms of nilpotent groups of class two with small rank
Authors: Fournelle Thomas A. 
Published: April 2009

AbstractRational abelian groups, that is, torsion-free abelian groups of rank one, are characterized by their types. This paper characterizes rational nilpotent groups of class two, that is, nilpotent groups of class two in which the center and central factor group are direct sums of rational abelian groups. This characterization is done according to the types of the summands of the center and the central factor group. Using these types and some cohomological techniques it is possible to determine the automorphism group of the nilpotent group in question by performing essentially matrix computations.In particular, the automorphism groups of rational nilpotent groups of class two and rank three are completely described. Specific examples are given of semicomplete and pseudocomplete nilpotent groups.
Another characterisation of Pfaffian bipartite graphs
Authors: Little Charles H. C. 
Published: April 2009

AbstractIt has been known for over twenty years that every planar graph is Pfaffian. Recently a characterisation of planar graphs in terms of strict maximal odd rings has been discovered. This paper attempts to elucidate the connection between the Pfaffian property and planarity by characterising Pfaffian bipartite graphs in terms of maximal odd rings.
Certain homomorphisms of the lattice of varieties of completely simple semigroups
Authors: Petrich Mario , Reilly Norman R. 
Published: April 2009

AbstractCompletely simple semigroups form a variety, , of algebras with the operations of multiplication and inversion. It is known that the mapping , where is the variety of all groups, is an isomorphism of the lattice of all subvarieties of onto a subdirect product of the lattice of subvarieties of and the interval . We consider embeddings of into certain direct products on the above pattern with rectangular bands, rectangular groups and central completely simple semigroups in place of groups.
Partial automorphisms and the reconstruction conjecture
Authors: Kocay W. L. 
Published: April 2009

AbstractLet Γ be a graph with isomorphic subgraphs G and H, and let θ: G → H be an isomorphism. If θ can be extended to an automorphism of Γ, we call θ a partial automorphism of Γ.We consider the application of partial automorphisms to the graph reconstruction conjecture, in particular, to the problem of reconstructing graphs with two vertices of degree k – 1 and the remaining vertices of degree k.
Cocompleteness over coverings
Authors: Betti Renato 
Published: April 2009

AbstractFor enriched categories the correct notion of limit involves indexing by a module. This paper studies the question of cocompletion for a given set of indexing modules. As well as providing a simplified treatment of cocompleteness for ordinary categories, associated sheaves and associated stacks are also included as cocompletion processes for appropriate bases. In fact the saturation of a general set of indexing modules has properties which justify our use of the term “covering” for members of the saturation.
Reducible 2 – (11, 5, 4) and 3 – (12, 6, 4) designs
Authors: Breach D. R. , Thompson A. R. 
Published: April 2009

AbstractOne way of constructing a 2 – (11,5,4) design is to take together all the blocks of two 2 – (11,5,2) designs having no blocks in common. We show that 58 non-isomorphic 2 – (11,5,4) designs can be so made and that through extensions by complementation these can be packaged into just 12 non-isomorphic reducible 3 – (12,6,4) designs.
Semigroups of constant maps
Authors: Schein Boris M. 
Published: April 2009

AbstractIn this paper “a map” denotes an arbitrary (everywhere defined, or partial, or even multi-valued) mapping. A map is constant if any two elements belonging to its domain have precisely the same images under this map. We characterize those semigroups which can be isomorphic to semigroups of constant maps or to involuted semigroups of constant maps.
Poisson convergence for point processes on the plane
Authors: Ivanoff B. Gail 
Published: April 2009

AbstractA compensator is defined for a point process in two dimensions. It is shown that a Poisson process is characterized by a continuous deterministic compensator. Sufficient conditions are given for convergence in distribution of a sequence of two-dimensional point processes in the Skorokhod topology to a Poisson process when the corresponding sequence of compensators converges pointwise in probability to a continuous deterministic function.
Homogeneous C*-algebras whose spectra are tori
Authors: Disney Shaun , Raeburn Iain 
Published: April 2009

AbstractBy a theorem of Fell and Tomiyama-Takesaki, an N-homogeneous C*-algebra with spectrum X has the form Γ(E) for some bundle E over X with fibre MN(C), and its isomorphism class is determined by that of E and its pull-backs f*E along homeomorphisms f of X. We describe the homogeneous C*-algebras with spectrum T2 or T3 by classifying the MN-bundles over Tk using elementary homotopy theory. We then use our results to determine the isomorphism classes of a variety of transformation group C*-algebras, twisted group C*-algebras and more general crossed products.
On semi-regularization topologies
Authors: Mršević M. , Reilly I. L. , Vamanamurthy M. K. 
Published: April 2009

AbstractThis paper discusses several properties of topological spaces and how they are refelected by corresponding properties of the associated semi-regularization topologies. For example a space is almost locally connected if and only if its semi-regularization is locally connected. Various separation, connectedness, covering, and mapping properties are considered.
Weakly prime one-sided ideals
Authors: Van Der Walt Andries P. J. 
Published: April 2009

AbstractA left ideal P in a ring is weakly prime if L, K ⊇ P and LK ⊆ P for left ideals L and K imply L = P or K = P. A prime left ideal is weakly prime but the converse is false. Characterizations of weakly prime left ideals as well as a number of their properties are obtained. The intersection of all the weakly prime left ideals in a ring is a left ideal which in general is contained in (but not equal to) the prime radical.
Near-rings of mappings on finite topological groups
Authors: Mason Gordon 
Published: April 2009

AbstractWhen G is a topological group, the set N(G) of continuous self-maps of G, and the subset N0(G) of those which fix the identity of G, are near-rings. In this paper we examine the (left) ideal structure of these near-rings when G is finite. N0(G) is shown to have exactly two maximal ideals, whose intersection is the radical. In the final section we investigate subnear-rings of N0(G) determined by certain continuous elements of the endomorphism near-ring.
Time-dependent Lipschitz attractors for non-semigroup evolution processes
Authors: Turinici Mihai 
Published: April 2009

AbstractA maximality principle on quasi-ordered pseudo-metric spaces is used to obtain a number of Lipschitz attraction results for non-semigroup evolution processes with respect to time-dependent families. As particular cases, a multivalued version of Dieudonné's means value theorem and the Kirk-Ray lipschitzianness test are derived.
A Schunck class construction and a problem concerning primitive groups
Authors: Förster Peter 
Published: April 2009

AbstractGaschütz has introduced the concept of a product of a Schunck class and a (saturated) formation (differing from the usual product of classes) and has shown that this product is a Schunck class provided that both of its factors consist of finite soluble groups. We investigate the same question in the context of arbitrary finite groups.
On finite groups whose 2-Sylow subgroups have cyclic subgroups of index 2
Authors: Wong W. J. 
Published: April 2009

If the finite group G has a 2-Sylow subgroup S of order 2a+1, containing a cyclic subgroup of index 2, then in general S may be one of the following six types [8]:(i) cyclic; (ii) Abelian of type (a, 1), a > 1; (iii) dihedral1; (iv) generalized quaternion; (v) {α, β}, α2a = β2, α2a−1+1, a ≧ 3;(vi) {α, β}, α2a = β2, α2a−1+1, a ≧ 3.
Thermal instability of Couette flow
Authors: Agrawal S. C. , Saini J. C. 
Published: April 2009

SummaryThe present paper investigates the thermal instability of a non-homogeneous fluid rotating between two co-axial cylinders when the inner cylinder is being heated uniformly. The conditions are established under which the oscillatory and non-oscillatory modes exist and further it has been shown that the oscillatory modes are amplified due to the adverse temperature gradient. In the case of non-oscillatory modes, sufficient conditions for stability and instability are obtained.
Quotient closed metanilpotent Fitting classes
Authors: Berger T. R. , Bryce R. A. , Cossey John 
Published: April 2009

AbstractA Fitting class of finite soluble groups is one closed under the formation of normal subgroups and products of normal subgroups. It is shown that the Fitting classes of metanilpotent groups which are quotient group closed as well are primitive saturated formuations.
The structure of a group of permutation polynomials
Authors: Mullen Gary L. , Niederreiter Harald 
Published: April 2009

AbstractLet Gq be the group of permutations of the finite field Fq of odd order q that can be represented by polynomials of the form ax(q+1)/2 + bx with a, b ∈ Fq. It is shown that Gq is isomorphic to the regular wreath product of two cyclic groups. The structure of Gq can also be described in terms of cyclic, dicyclic, and dihedral groups. It also turns out that Gq is isomorphic to the dymmetry group of a regular complex polygon.
Monoidal closed structures on categories with constant maps
Authors: Logar Alessandro , Rossi Fabio 
Published: April 2009

AbstractThe purpose of this paper is to study the so-called canonical monoidal closed structures on concrete categories with constant maps. First of all we give an example of a category of this kind where there exists a non canonical monoidal closed structure. Later, we give a technique to construct a class of suitable full subcategories of the category of T0-spaces, such that all monoidal closed structures on them are canonical. Finally we show that “almost all” useful categories of topological compact spaces admit no monoidal closed structures whatsoever.
Almost all chordal graphs split
Authors: Bender E. A. , Richmond L. B. , Wormald N. C. 
Published: April 2009

AbstractA chordal graph is a graph in which every cycle of length at least 4 has a chord. If G is a random n-vertex labelled chordal graph, the size of the larget clique in about n/2 and deletion of this clique almost surely leaves only isolated vertices. This gives the asymptotic number of chordal graphs and information about a variety of things such as the size of the largest clique and connectivity.
Nil and s-prime Ω-groups
Authors: Buys A. , Gerber G. K. 
Published: April 2009

AbstractThe concepts nilpotent element, s-prime ideal and s-semi-prime ideal are defined for Ω-groups. The class {G|G is a nil Ω-group} is a Kurosh-Amitsur radical class. The nil radical of an Ω-group coincides with the intersection of all the s-prime ideals. Furthermore an ideal P of G is an s-semi-prime ideal if and only if G/P has no non-zero nil ideals.