bluuebunny/crossref_metadata_2025_split huggingface dataset:
Essentially closed radical classes
Authors: Loi N. V. 
Published: April 2009

AbstractThe main goal of this paper is to describe radical classes closed under essential extensions. It turns out that such classes are precisely the homomorphically closed semisimple classes, and hence a radical class is essentially closed if and only if it is subdirectly closed. Moreover, a class is closed under homomorphic images, direct sums and essential extensions if and only if it is an essentially closed radical class. Also radical classes are investigated which are closed under Dorroh essentially extensions only, such a radical class R consists of idempotent rings provided that R does not contain the ring of integers, meanwhile all the other radicals satisfy this requirement. A description of (hereditary and) Dorroh essentially closed radicals is given in Theorem 4.
Measurability of functions of two variables
Authors: Michael J. H. , Rennie B. C. 
Published: April 2009

SummaryThis paper investigates the existence and equality of the double and repeated integrals of a real function on a plane set. The main result (Theorem 2) is that if a function on a plane Lebesgue measurable set is continuous in one variable and measurable in the other then it is measurable in the plane.
Mildly distributive semilattices
Authors: Hickman Robert 
Published: April 2009

AbstractThere is no single generalization of distributivity to semilattices. This paper investigates the class of mildly distributive semilattices, which lies between the two most commonly discussed classes in this area—weakly distributive semilattices and distributive semilattices. Particular attention is paid to describing and characterizing congruence distributive mildly distributive semilattices, in contrast to distributive semilattices, whose lattice of join partial congruences is badly behaved and which are difficult to describe.
A note on the Levitzki radical of a near-ring
Authors: Groenewald N. J. , Potgieter P. C. 
Published: April 2009

AbstractIt is known that in a near-ring N the Levitzki radical L(N), that is, the sum of all locally nilpotent ideals, is the intersection of all the prime ideals P in N such that N/P has zero Levitzki radical. The purpose of this note is to prove that L(N) is the intersection of a certain class of prime ideals, called l-prime ideals. Every l-prime ideal P is such that N/P has zero Levitzki radical. We also introduce an l-semi-prime ideal and show that P is an l-semi-prime ideal if and only if N/P has zero Levitzki radical. We get another characterization of the Levitzki radical of the near-ring as the intersection of all the l-semi-prime ideals.
Cohomology and extensions of regular semigroups
Authors: Loganathan M. 
Published: April 2009

AbstractLet S be a regular semigroup and A a D(S)-module. We proved in a previous paper that the set Ext(S, A) of equivalence classes of extensions of A by S admits an abelian group structure and studied its functorial properties. The main aim of this paper is to describe Ext(S, A) as a second cohomology group of certain chain complex.
Addition of an identity to an ordered Banach space
Authors: Robinson Derek W. , Yamamuro Sadayuki 
Published: April 2009

AbstractGiven an ordered Banach space ℬ equipped with an order-norm we construct a larger space ℬ¯ with an order-norm and order-identity such that B is isometrically order-isomorphic to a Banach subspace of B. We also discuss the extension of positive operators from ℬto ℬ¯.
On p-adic F-functions
Authors: Lianxiang Wang 
Published: April 2009

AbstractWe introduce the class of p-adic F-functions which contains both the p-adic E-function and p-adic G-functions, as well as other functions. In this paper we obtain lower bounds for polynomials in the values at algebraic points of a class of p-adic F-functions defined over the completion of the algebraic closure of a p-adic field.
One more method to construct the irreducible unitary representations of nipotent Lie groups
Authors: Astaneh A. A. 
Published: April 2009

AbstractIn this paper one more canonical method to construct the irreducible unitary representations of a connected, simply connected nilpotent Lie group is introduced. Although we used Kirillov' analysis to deduce this procedure, the method obtained differs from that of Kirillov's, in that one does not need to consider the codjoint representation of the group in the dual of its Lie algebra (in fact, neither does one need to consider the Lie algebra of the group, provided one knows certain connected subgroups and their characters). The method also differs from that of Mackey's as one only needs to induce characters to obtain all irreducible representations of the group.
Isomorphic subgraphs having minimal intersections
Authors: Mullin R. C. , Roy B. K. , Schellenberg P. J. 
Published: April 2009

AbstractGiven a finite graph H and G, a subgraph of it, we define σ (G, H) to be the largest integer such that every pair of subgraphs of H, both isomorphic to G, has at least σ(G, H) edges in common; furthermore, R(G, H) is defined to be the maximum number of subgraphs of H, all isomorphic to G, such that any two of them have σ(G, H) edges common between them. We are interested in the values of σ(G, H) and R(G, H) for general H and G. A number of combinatorial problems can be considered as special cases of this question; for example, the classical set-packing problem is equivalent to evaluating R (G, H) where G is a complete subgraph of the complete graph H and σ(G, H) = 0, and the decomposition of H into subgraphs isomorphic to G is equivalent to showing that σ(G, H) = 0 and R(G, H) = ε(H)/ε(G) where ε(H), ε(G) are the number of edges in H, G respectively.A result of S. M. Johnson (1962) gives an upper bound for R(G, H) in terms of σ(G, H). As a corollary of Johnson's result, we obtain the upper bound of McCarthy and van Rees (1977) for the Cordes problem. The remainder of the paper is a study of σ (G, H) and R(G, H) for special classes of graphs; in particular, H is a complete graph and G is, in most instances, a union of disjoint complete subgraphs.
2-Groups of almost maximal class: corrigendum
Authors: James Rodney 
Published: April 2009

On page 354 of James (1975) (in the proof of Theorem 5.3(b)) there appear the following two sentences:‘When n≥7, replacewe may suppose δ=0.’Unfortunately, the second sentence does not follow from the first. In fact, the first sentence also forces us to replace remains unaltered. Thus the case δ=1 is omitted in the paper.
On transitive permutation groups with a subgroup satisfying a certain conjugacy condition
Authors: Praeger Cheryl E. 
Published: April 2009

AbstractLet G be transitive permutation group of degree n and let K be a nontrivial pronormal subgroup of G (that is, for all g in G, K and Kg are conjugate in (K, Kg)). It is shown that K can fix at most ½(n – 1) points. Moreover if K fixes exactly ½(n – 1) points then G is either An or Sn, or GL(d, 2) in its natural representation where n = 2d-1 ≥ 7. Connections with a result of Michael O'Nan are dicussed, and an application to the Sylow subgroups of a one point stabilizer is given.
A general measure decomposition theorem by means of the generalized wallman remainder
Authors: Bachman George , Stratigos Panagiotis D. 
Published: April 2009

AbstractLet ℒ be a lattice of subsets of a setX. LetMR(ℒ) denote the set of all ℒ-regular (finitely additive) measures on the algebra generated by ℒ. Under the assumption that ℒ is disjunctive, in the first part of the paper, criteria are obtained for the σ-smoothness, τ-smoothness, and tightness of elements ofMR(ℒ) in terms of the general Wallman remander. in the second part of the paper, various applications are given, and, in particular, extensions and refinements of the Yoside-Hewitt Decom position Theorem are obtained.
Expectation values of operators in the quasi-chemical equilibrium theory part II
Authors: Blatt John M. 
Published: April 2009

AbstractExpectation values of one-particle and two-particle operators are evaluated in the quasi-chemical equilibrium (pair correlation) approximation to statistical mechanics. Earlier work was restricted to the case of extreme Bose-Einstein condensation of the correlated pairs; the new formulas are not so restricted, but are correspondingly more complicated to evaluate practically. However, a simple result can be obtained for the expectation value of the number of particles.
Relatively central operators on Archimedean vector lattices II
Authors: McPolin P. T. N. , Wickstead A. W. 
Published: April 2009

AbstractWe continue the study of operators from an Archimedean vector lattice E into a cofinal sublattice H which have the property that there is λ > 0 such that if x ∈ E, h ∈ H and |x|≤|h|, then |Tx| ≤ λ|h|. The collection Z(E|H) of all of those operators forms an algebra under composition. We investigate the relationship between the properties of having an identity, being Abelin and being semi-simple for such-algebras, culminating in a proof that they are equivalent if H is Dedekind complete. We also study various for such an operator T, showing that, apart from 0, its spectrum relative to Z(E|H) is the same as that of T|H relative to Z(H) and that of T relative to ℒ(E) (Provided E is a Banach lattice and H is closed).
Free products of topological groups with a closed subgroup amalgamated
Authors: Nickolas Peter 
Published: April 2009

AbstractIt is shown that if {Gn: n = 1, 2,…} is a countable family of Hausdorff kω-topological groups with a common closed subgroup A, then the topological amalgamated free product *AGn exists and is a Hausdorff kω-topological group with each Gn as a closed subgroup. A consequence is the theorem of La Martin that epimorphisms in the category of kω-topological groups have dense image.
A note on a method of Milne-Thomson
Authors: Buchwald V. T. 
Published: April 2009

AbstractMilne-Thomson has used the method of analytic continuation to solve boundary value problems of the annulus in plane elastostatics. However, his use of Cauchy integrals is incorrect, and it is shown in this note that the solution is obtained in terms of Laurent Series expansions. The solution is equivalent to that of Muskhelishvili, but is simpler to use in some applications.A similar approach is used to solve the boundary value problem of the infinite strip, the solution being given in terms of functions of a complex variable expressed as Fourier integrals.
The transient behaviour of the queueing system Gi/M/1
Authors: Brockwell P. J. 
Published: April 2009

SUMMARYWe consider a single server queue for which the interarrival times are identically and independently distributed with distribution function A(x) and whose service times are distributed independently of each other and of the interarrival times with distribution function B(x) = 1 − e−x, x ≧ 0. We suppose that the system starts from emptiness and use the results of P. D. Finch [2] to derive an explicit expression for qnj, the probability that the (n + 1)th arrival finds more than j customers in the system. The special cases M/M/1 and D/M/1 are considerend and it is shown in the general case that qnj is a partial sum of the usual Lagrange series for the limiting probability .
Uniform estimates for families of singular integrals and double Fourier series
Authors: Prestini Elena 
Published: April 2009

AbstractIt is an open problem to establish whether or not the partial sums operator SNN2f(x, y) of the Fourier series of f ∈ Lp, 1 < p < 2, converges to the function almost everywhere as N → ∞. The purpose of this paper is to identify the operator that, in this problem of a.e. convergence of Fourier series, plays the central role that the maximal Hilbert transform plays in the one-dimensional case. This operator appears to be a singular integral with variable coefficients which is a variant of the maximal double Hilbert transform.
On quasidifferentiable optimization
Authors: Craven B. D. 
Published: April 2009

AbstractLagrangian necessary conditions for optimality, of both Fritz John and Kuhn Tucker types, are obtained for a constrained minimization problem, where the functions are locally Lipschitz and have directional derivatives, but need not have linear Gâteaux derivatives; the variable may be constrained to lie in a nonconvex set. The directional derivatives are assumed to have some convexity properties as functions of direction; this generalizes the concept of quasidifferentiable function. The convexity is not required when directional derivatives are replaced by Clarke generalized derivatives. Sufficient Kuhn Tucker conditions, and a criterion for the locally solvable constraint qualification, are obtained for directionally differentiable functions.
Cartan-Whitehead decomposition as Adams cocompletion
Authors: Behera A. , Nanda S. 
Published: April 2009

AbstractDeleanu, Frei and Hilton have developed the notion of generalized Adams completion in a categorical context; they have also suggested the dual notion, namely, the Adams cocompletion of an object in a category. In this paper the different stages of the Cartan-Whitehead decomposition of a 0-connected space are shown to be the cocompletions of the space with respect to suitable sets of morphisms.
Monogenic normal systems are universal
Authors: Arbib Michael A. 
Published: April 2009

AbstractIn 1943, Post conjectured that “monogenic normal systems are universal”, and in 1961 Minsky proved a stronger result “‘tag’ systems are universal” which implied the proof of Post's conjecture. The author had independently obtained a simple direct proof of Post's conjecture. The purpose of this note, then, is to present an exposition of Post's conjecture, and to show the full simplicity of its direct verification.
Altitudes of a general n–simplex
Authors: Mandan Sahib Ram 
Published: April 2009

AbstractThe purpose of this paper is to prove that the altitudes of an n-simplex (a simplexin an n-space) S form an associated set of n+1 lines (see Baker, [4] for n = 4) such that any (n–2)-space meeting n of them meets the (n+1)th too. As an immediate consequence 2 quadrics are associated with S, one touching its primes at the respective feet of its altitudes and the other touching n(n+1) primes, n parallel to each of its altitudes and 2 through each of its (n−2)-spaces. Certain special cases are also mentioned.
An analogue of the Hadamard conjecture for n × n matrices with n ≡2 (mod 4)
Authors: Little Charles H. C. 
Published: April 2009

AbstractIt is known that the problem of settling the existence of an n × n Hadamard matrix, where n is divisible by 4, is equivalent to that of finding the cardinality of a smallest set T of 4-circuits in the complete bipartite graph Kn, n such that T contains at least one circuit of each copy of K2,3 in Kn, n. Here we investigate the case where n ≡ 2 (mod 4), and we show that the problem of finding the cardinality of T is equivalent to that of settling the existence of a certain kind of n × n matrix. Moreover, we show that the case where n ≡ 2 (mod 4) differs from that where n ≡ 0 (mod 4) in that the problem of finding the cardinality of T is not equivalent to that of maximising the determinant of an n × n (1,-1)-matrix.
Growth sequences of finite semigroups
Authors: Wiegold James , Lausch H. 
Published: April 2009

AbstractThe growth sequence of a finite semigroup S is the sequence {d(Sn)}, where Sn is the nth direct power of S and d stands for minimum generating number. When S has an identity, d(Sn) = d(Tn) + kn for all n, where T is the group of units and k is the minimum number of generators of S mod T. Thus d(Sn) is essentially known since d(Tn) is (see reference 4), and indeed d(Sn) is then eventually piecewise linear. On the other hand, if S has no identity, there exists a real number c > 1 such that d(Sn) ≥ cn for all n ≥ 2.
On Fixed Points of Asymptotically Regular Mappings
Authors: Rhoades B. E. , sessa S. , Khan M. S. , Swaleh M. 
Published: April 2009

Some results on fixed points of asymptotically regular mappings are obtained in complete metric spaces and normed linear spaces.The structure of the set of common fixed points is also discussed in Banach spaces. Our work generalizes essentially known results of Das and Naik, Fisher, Jaggi, Jungck, Rhoades, Singh and Tiwari and several others.
Chief Series and Right Regular Representations of Finite p-Groups
Authors: Leinen Felix 
Published: April 2009

AbstractWe study the embeddings of a finite p-group U into Sylow p-subgroups of Sym (U) induced by the right regular representation p: U→ Sym(U). It turns out that there is a one-to-one correspondence between the chief series in U and the Sylow p-subgroups of Sym (U) containing Up. Here, the Sylow p-subgroup Pσ of Sym (U) correspoding to the chief series σ in U is characterized by the property that the intersections of Up with the terms of any chief series in Pσ form σp. Moreover, we see that p: U→ Pσ are precisely the kinds of embeddings used in a previous paper to construct the non-trivial countable algebraically closed locally finite p-groups as direct limits of finite p-groups.
Almost everywhere convergence of lacunary trigonometric series with respect to Riesz products
Authors: PeyriÈre J. 
Published: April 2009

AbstractLet {λj}j≥0 be a sequence of positive integers such that λj+1/λj≥3 and {aj}j≥0 a sequence of complex numbers such that |aj|≤1. Let μ be the Riesz product πj≥0[1+ Re(ajeiλjx)], that is, the weak limit of measures on T the density of which are the partial products. Then if Σj≥0|aj|2≤∞ the series Σj≥0 aj(eiλjx - ½āj) converges for μ-almost every x. The μ-a.e. convergence of series Σ ajeinλjx is also investigated as well as the case of Riesz products on a compact commutative group.
Factorization of invertible matrices over rings of stable rank one
Authors: Vaserstein Leonid N. , Wheland Ethel 
Published: April 2009

AbstractEvery invertible n-by-n matrix over a ring R satisfying the first Bass stable range condition is the product of n simple automorphisms, and there are invertible matrices which cannot be written as the products of a smaller number of simple automorphisms. This generalizes results of Ellers on division rings and local rings.
On immersions of N-manifolds in codimension N − 1
Authors: Aguilar M. A. , Pastor G. 
Published: April 2009

AbstractWe give a simple proof, using only classical algebraic topology, of the following theorem of B. H. Li and F. P. Peterson. Any map from an N-manifold into a (2N − 1)-manifold is homotopic to an immersion.
On measurable multifunctions with stochastic domain
Authors: Papageorgiou Nikolaos S. 
Published: April 2009

AbstractIn this paper we prove several random fixed point theorems for multifunctions with a stochastic domain. Then those techniques are used to establish the existence of solutions for random differential inclusions. A useful tool in this process is a stochastic version of the Tietze extension theorems that we prove. Finally we present a stochastic version of the Riesz representation theorem for Hilbert spaces.
Operators related to idempotent generated and monoid completely regular semigroups
Authors: Petrich Mario , Reilly Norman R. 
Published: April 2009

AbstractThe class CR of completely regular semigroups (unions of groups or algebras with the associative binary operation of multiplication and the unary operation of inversion subject to the laws x = xx-1, (x−1)-1 = x and xx-1 = x-1x) is a variety. Among the important subclasses of CR are the classes M of monoids and I of idempotent generated members. For each C ∈ {I, M}, there are associated mappings ν → ν ∩ C and ν → (Ν ∩ C), the variety generated by ν ∩ C. The lattice theoretic properties of these mappings and the interactions between these mappings are studied.
The lattice of completely regular semigroup varieties
Authors: Pastijn Francis 
Published: April 2009

AbstractA completely regular semigroup is a semigroup which is a union of groups. The class CR of completely regular semigroups forms a variety. On the latticeL(CR) of completely regular semigroup varieties we define two closure operations which induce complete congruences. The consideration of a third complete congruence onL(CR) yields a subdirect decomposition ofL(CR). Using these results we show thatL(CR) is arguesian. This confirms the (tacit) conjecture thatL(CR) is modular.
Weakly reductive semigroups with atomistic congruence lattices
Authors: Auinger Karl 
Published: April 2009

AbstractThe structure of semigroups with atomistic congruence lattices (that is, each congruence is the supremum of the atoms it contains) is studied. For the weakly reductive case the problem of describing the structure of such semigroups is solved up to simple and congruence free semigroups, respectively. As applications, all commutative, finite, completely semisimple semigroups, respectively, with atomistic congruence lattices are described.
Varieties of groups and isologisms
Authors: Hekster N. S. 
Published: April 2009

AbstractIn order to classify solvable groups Philip Hall introduced in 1939 the concept of isoclinism. Subsequently he defined a more general notion called isologism. This is so to speak isoclinism with respect to a certain variety of groups. The equivalence relation isologism partitions the class of all groups into families. The present paper is concerned with the internal structure of these families.
Rational solutions of linear differential equations
Authors: Bezivin J.-P. , Robba P. 
Published: April 2009

AbstractLetLbe a linear differential operator with rational coefficients such that 0 is not an irregular singularity ofLand that for sufficiently manyp's the equationLv= 0 has no zero solution modp. We show that ifuis a formal power series whose coefficients are p-adic integers for almost allpand ifLuis rational, thenutoo is rational.
The asymmetric product of three inhomogeneous linear forms
Authors: Grover V. K. 
Published: April 2009

AbstractLet Λ be a lattice in R3 of determinant 1. Define the homogeneous minium of Λ as mn (Λ) = inf |u1, u2, u3| extended over all points (u1, u2, u3) of Λ other than the origin. It is shown that for any given (c1, c2, c3) in R3 there exists a point (u1, u2, u3) of Λ for which provided that ρσ > 1/64 if mn (Λ) = 0, and ρσ ≥1/16.81 if mn (A) > 0.
Fractional powers of generators of equicontinuous semigroups and fractional derivatives
Authors: Lanford Oscar E. , Robinson Derek W. 
Published: April 2009

AbstractWe analyze fractional powersHα, α > 0, of the generatorsHof uniformly bounded locally equicontinuous semigroupsS. TheHαare defined as the αth derivative δαof the Dirac measure δ evaluated onS. We demonstrate that theHαare closed operators with the natural properties of fractional powers, for example,HαHβ=Hα+βfor α, β > 0, and (Hα)β=Hαβfor 1 > α > 0 and β > 0. We establish thatHα can be evaluated by the Balakrishnan-Lions-Peetre algorithmwheremis an integer larger than α,Cα, mis a suitable constant, and the limit exists in the appropriate topology if, and only if,x ∈ D(Hα). Finally we prove thatH∈is the fractional derivation ofSin the sensewhere the limit again exists if, and only if,x∈ D(Hα).
Archimedes integrals and conuclear spaces
Authors: Jefferies B. , Okada S. 
Published: April 2009

AbstractThe lack of completeness with respect to the semivariation norm, of the space of Banach space valued functions, Pettis integrable with respect to a measure μ, often impedes the direct extension of results involving integral representations, true in the finite-dimensional setting, to the general vector space setting. It is shown here that the space of functions with values in a space Y, μ-Archimedes integrable in a Banach space X embedded in Y, is complete with respect to convergence in semivariation, provided the embedding from X into Y is completely summing. The result is applied to the case when Y is a conuclear space, in particular, when X is a function space continuously included in a space of distributions.