bluuebunny/crossref_metadata_2025_split huggingface dataset:
On unilateral shift operators and C0-operators
Authors: Jung Il Bong , Kim Yong Chan 
Published: April 2009

AbstractLet S(n) be a unilateral shift operator on a Hilbert space of multiplicity n. In this paper, we prove a generalization of the theorem that if S(1) is unitarily equivalent to an operator matrix form relative to a decomposition ℳ ⊕ N, then E is in a certain class C0 which will be defined below.
Möbius covariance of iterated Dirac operators
Authors: Peetre Jaak , Qian Tao 
Published: April 2009

AbstractUsing Fourier transforms, we give a new proof of certain identites for the fundamental solutions of the iterated Dirac operators and Ḏl = (Σ/Σx0 + Ḏ)l. Based on the close relationship between the fundamental solutions and the conformal weights we then give a simple proof of B. Bojarski's results on the conformal covariance of Ḏl. We also prove a new conformal covatiance result of D.
On finite ρ-groups with isomorphic maximal subgroups
Authors: Hermann Peter Z. 
Published: April 2009

AbstractFinite ρ-groups with all of their maximal subgroups isomorphic are studied by means of the coclass. All such groups of coclass I and 2 are determined, while those of coclass 3 are shown to have order at most ρ13. A general bound for the order is given as a function of ρ and the coclass only.
The persistence of logconcavity for positive solutions of the one dimensional heat equation
Authors: Keady G. 
Published: April 2009

AbstractConsider positive solutions of the one dimensional heat equation. The space variablexlies in (–a, a): the time variabletin (0,∞). When the solutionusatisfies (i)u (±a, t)= 0, and (ii)u(·, 0) is logconcave, we give a new proof based on the Maximum Principle, that, for any fixedt > 0, u(·, t)remains logconcave. The same proof techniques are used to establish several new results related to this, including results concerning joint concavity in (x, t) similar to those considered in Kennington [15].
Imbedded subgroups of abelian groups
Authors: Berlinghoff W. P. , Moore J. D. , Reid J. D. 
Published: April 2009

AbstractA subgroupHof an abelianp–groupGis pure inGif the inclusion map ofHintoGis an isometry with respect to the (pseudo-) metrics onHandGassociated with theirp–adic topologies. In this paper, those subgroups (called here imbedded subgroups) of abelian groups for which the inclusion is a homeomorphism with respect to thep–adic topologies are studied, the aim being to compare the concepts of imbeddedness and purity. Perhaps the main results indicate that imbedded subgroups are considerably more abundant than pure subgroups. Groups for which this is not the case are characterized.
On presentation of PSL (2, pn)
Authors: Campbell C. M. , Robertson E. F. , Williams P. D. 
Published: April 2009

AbstractWe give presentations for the groups PSL(2, pn), p prime, which show that the deficiency of these groups is bounded below. In particular, for p = 2 where SL(2, 2n) = PSL(2, 2n), we show that these groups have deficiency greater than or equal to – 2. We give deficiency – 1 presentations for direct products of SL(2, 2n) for coprime ni. Certain new efficient presentations are given for certain cases of the groups considered.
Uncertainty principles like Hardy's theorem on some Lie groups
Authors: Bagchi S. C. , Ray Swagato K. 
Published: April 2009

AbstractWe extend an uncertainty principle due to Cowling and Price to Euclidean spaces, Heisenberg groups and the Euclidean motion group of the plane. This uncertainty principle is a generalisation of a classical result due to Hardy. We also show that on the real line this uncertainty principle is almost equivalent to Hardy's theorem.
An algebraic approach to Wigner's unitary-antiunitary theorem
Authors: Molnár Lajos 
Published: April 2009

AbstractWe present an operator algebraic approach to Wigner's unitary-antiunitary theorem using some classical results from ring theory. To show how effective this approach is, we prove a generalization of this celebrated theorem for Hilbert modules over matrix algebras. We also present a Wigner-type result for maps on primeC*-algebras.
Hilbert transform associated with finite maximal subdiagonal algebras
Authors: Randrianantoanina Narcisse 
Published: April 2009

AbstractLet ℳ be a von Neumann algebra with a faithful normal trace τ, and let H∞ be a finite, maximal. subdiagonal algebra of ℳ. We prove that the Hilbert transform associated with H∞ is a linear continuous map from L1 (ℳ, τ) into L1.∞ (ℳ, τ). This provides a non-commutative version of a classical theorem of Kolmogorov on weak type boundedness of the Hilbert transform. We also show that if a positive measurable operator b is such that b log+b ∈ L1 (ℳ, τ) then its conjugate b, relative to H∞ belongs to L1 (ℳ, τ). These results generalize classical facts from function algebra theory to a non-commutative setting.
Character degrees and nilpotence class in p-groups
Authors: Slattery Michael C. 
Published: April 2009

AbstractWork of Isaacs and Passman shows that for some sets X of integers, p-groups whose set of irreducible character degrees is precisely X have bounded nilpotence class, while for other choices of X, the nilpotence class is unbounded. This paper presents a theoren which shows some additional sets of character degrees which bound nilpotence class within the family of metabelian p-groups. In particular, it is shown that is the non-linear irreducible character degrees of G lie between pa and pb, where a ≤ b ≤ 2a − 2, then the nilpotence class of G is bounded by a function of p and b − a.
The π-character theory of solvable groups
Authors: Isaacs I. M. 
Published: April 2009

AbstractThere is a deeper structure to the ordinary character theory of finite solvable groups than might at first be apparent. Mauch of this structure, which has no analog for general finite gruops, becomes visible onyl when the character of solvable groups are viewes from the persepective of a particular set π of prime numbers. This purely expository paper discusses the foundations of this πtheory and a few of its applications. Included are the definitions and essential properties of Gajendragadkar's π-special characters and their connections with the irreducible πpartial characters and their associated Fong characters. Included among the consequences of the theory discussed here are applications to questions about the field generated by the values of a character, about extensions of characters of subgroups and about M-groups.
Regular maps with small parameters
Authors: Conder Marston 
Published: April 2009

AbstractRegular maps of type {p, q}r and the associated groups Gp,q,r are considered for small values for p, q and r. In particular, it is shown that the groups G4,6,6 and G5,5,6 are Abelian-by-infinite, and there are infinitely many regular maps of each of the types {4, 6}6, {5, 5}6, {5, 6}6 and {6, 6}6.
Vertex-primitive half-transitive graphs
Authors: Taylor D. E. , Xu Ming-Yao 
Published: April 2009

AbstractGiven an infinite family of finite primitive groups, conditions are found which ensure that almost all the orbitals are not self-paired. If p is a prime number congruent to ±1(mod 10), these conditions apply to the groups P S L (2, p) acting on the cosets of a subgroup isomorphic to A5. In this way, infinitely many vertex-primitive ½-transitive graphs which are not metacirculants are obtained.
Extending abelian groups to rings
Authors: Batten Lynn M. , Coulter Robert S. , Henderson Marie 
Published: April 2009

AbstractFor any abelian group G and any function f: G → G we define a commutative binary operation or ‘multiplication’ on G in terms of f. We give necessary and sufficient conditions on f for G to extend to a commutative ring with the new multiplication. In the case where G is an elementary abelian p–group of odd order, we classify those functions which extend G to a ring and show, under an equivalence relation we call weak isomorphism, that there are precisely six distinct classes of rings constructed using this method with additive group the elementary abelian p–group of odd order p2.
A note on the boundedness of Bergman-type operators on mixed norm spaces
Authors: Lou Zengjian 
Published: April 2009

AbstractWe prove the boundedness of Bergman-type operators on mixed norm spaces Lp·q (φ) for 0 < q < 1 and 0 < p ≤ ∞ of functions on the unit ball of ” with an application to Gleason's problem.
Extinction and explosion of nonlinear Markov branching processes
Authors: Pakes Anthony G. 
Published: April 2009

AbstractThis paper concerns a generalization of the Markov branching process that preserves the random walk jump chain, but admits arbitrary positive jump rates. Necessary and sufficient conditions are found for regularity, including a generalization of the Harris-Dynkin integral condition when the jump rates are reciprocals of a Hausdorff moment sequence. Behaviour of the expected time to extinction is found, and some asymptotic properties of the explosion time are given for the case where extinction cannot occur. Existence of a unique invariant measure is shown, and conditions found for unique solution of the Forward equations. The ergodicity of a resurrected version is investigated.
The exact order of generalized diaphony and multidimensional numerical integration
Authors: Lev Vsevolod F. 
Published: April 2009

AbstractFor a point set in the multidimensional unit torus we introduce an Lk-measure of uniformity of distribution, which for k=2 reduces to diaphony (and thus in this case essentially coincides with Weyl L2-discrepancy). For k ∈ [1, 2] we establish a sharp asymptotic for this new measure as the number of points of the set tends to infinity. Upper and lower-bound estimates are given also for k >2.
On the value distribution of iterated entire functions
Authors: Jian-Hua Zheng 
Published: April 2009

AbstractLet f be a transcendental entire function and denote the n-th iterate fn. For n ≥ 2, we give an explict estimate of the number of periodic points of f with period n, that is, fix-points of fn which are not fix-points of fk for 1 ≤ k <n.
Non-embeddings of the real flag manifolds RF (1, 1,n– 2)
Authors: Ajayi Deborah O. , Ilori Samuel A. 
Published: April 2009

AbstractThis paper gives non-embeddings and non-immersions for the real flag manifolds RF(1, 1,n–2), n > 3 and shows that Lam's immersions forn= 4 and 5 and Stong's result forn= 6 are the best possible.
The domain space of an analytic composition operator
Authors: Domenig Thomas , Jarchow Hans , Riedl Reinhard 
Published: April 2009

AbstractIn this paper we show that, for analytic composition operators between weighted Bergman spaces (including Hardy spaces) and as far as boundedness, compactness, order boundedness and certain summing properties of the adjoint are concerned, it is possible to modify domain spaces in a systematic fashion: there is a space of analytic functions which embeds continuously into each of the spaces under consideration and on which the above properties of the operator are decided.A remarkable consequence is that, in the setting of composition operators between weighted Bergman spaces, the properties in question can be identified as properties of the operator as a map between appropriately chosen Hilbert spaces.
Direct and converse inequalities for positive linear operators on the positive semi-axis
Authors: Adell José A. , Sangüesa Carmen 
Published: April 2009

AbstractWe consider positive linear operators of probabilistic typeL1facting on real functionsfdefined on the positive semi-axis. We deal with the problem of uniform convergence ofL1ftof, both in the usual sup-norm and in a uniformLptype of norm. In both cases, we obtain direct and converse inequalities in terms of a suitable weighted first modulus of smoothness off. These results are applied to the Baskakov operator and to a gamma operator connected with real Laplace transforms, Poisson mixtures and Weyl fractional derivatives of Laplace transforms.
Partial characters with respect to a normal subgroup
Authors: Navarro Gabriel , Sanus Lucia 
Published: April 2009

AbstractSuppose that G is a π-separable group. Let N be a normal π1-subgroup of G and let H be a Hall π-subgroup of G. In this paper, we prove that there is a canonical basis of the complex space of the class functions of G which vanish of G-conjugates ofHN. When N = 1 and π is the complement of a prime p, these bases are the projective indecomposable characters and set of irreduciblt Brauer charcters of G.
An extension of the principle of spatial averaging for inertial manifolds
Authors: Kwean Hyukjin 
Published: April 2009

AbstractIn this paper we extend a theorem of Mallet-Paret and Sell for the existence of an inertial manifold for a scalar-valued reaction diffusion equation to new physical domains ωn ⊂ Rn, n = 2,3. For their result the Principle of Spatial Averaging (PSA), which certain domains may possess, plays a key role for the existence of an inertial manifold. Instead of the PSA, we define a weaker PSA and prove that the domains φn with appropriate boundary conditions for the Laplace operator, δ, satisfy a weaker PSA. This weaker PSA is enough to ensure the existence of an inertial manifold for a specific class of scalar-valued reaction diffusion equations on each domain ωn under suitable conditions.
On two pairs of non-self hybrid mappings
Authors: Ćirić Ljubomir B. , Sheok Ume Jeong , Nikolić Nebqjša T. 
Published: April 2009

AbstractAbstrac In this paper we obtain some results on coincidence and common fixed points for two pairs of multi-valued and single-valued non-self mappings in complete convex metric spaces. We improve on previously used methods of proof and obtain results for mappings which are not necessarily compatible and not necessarily continuous, generalizing some known results. In particular, a theorem by Rhoades [19] and a theorem by Ahmed and Rhoades [2] are generalized and improved.
Rate of escape of random walks on free products
Authors: Gilch Lorenz A. 
Published: April 2009

AbstractSuppose we are given the free product V of a finite family of finite or countable sets (Vi)i∈∮and probability measures on each Vi, which govern random walks on it. We consider a transient random walk on the free product arising naturally from the random walks on the Vi. We prove the existence of the rate of escape with respect to the block length, that is, the speed at which the random walk escapes to infinity, and furthermore we compute formulae for it. For this purpose, we present three different techniques providing three different, equivalent formulae.
An Open Mapping Theorem For Pro-Lie Groups
Authors: Hofmann Karl H. , Morris Sidney A. 
Published: April 2009

AbstractA pro-Lie group is a projective limit of finite dimensional Lie groups. It is proved that a surjective continuous group homomorphism between connected pro-Lie groups is open. In fact this remains true for almost connected pro-Lie groups where a topological group is called almost connected if the factor group modulo the identity component is compact. As consequences we get a Closed Graph Theorem and the validity of the Second Isomorphism Theorem for pro-Lie groups in the almost connected context.
Canonical Varieties of Completely Regular Semigroups
Authors: Petrich Mario 
Published: April 2009

AbstractCompletely regular semigroups CR are regarded here as algebras with multiplication and the unary operation of inversion. Their lattice of varieties is denoted by L(CR). Let B denote the variety of bands and L(B) the lattice of its subvarieties. The mapping V → V ∩ B is a complete homomorphism of L(CR) onto L(B). The congruence induced by it has classes that are intervals, say VB = [VB, VB] for V ∈ L(CR). Here VB = V ∩ B. We characterize VB in several ways, the principal one being an inductive way of constructing bases for v-irreducible band varieties. We term the latter canonical. We perform a similar analysis for the intersection of these varieties with the varieties BG, OBG and B.
Unique factorization in the ring R[x]
Authors: Beauregard Raymond A. 
Published: April 2009

AbstractIf R is a commutative unique factorization domain (UFD) then so is the ring R[x]. If R is not commutative then no such result is possible. An example is given of a bounded principal right and left ideal domain R, hence a similarity-UFD, for which the polynomial ring R[x] in a central indeterminate x is not a UFD in any reasonable sense. On the other hand, it is shown that if R is an invariant UFD then R[x] is a UFD in an appropriate sense.
Some fixed point theorems
Authors: Subrahmanyam P. V. , Reilly I. L. 
Published: April 2009

AbstractBanach's contraction principle guarantees the existence of a unique fixed point for any contractive selfmapping of a complete metric space. This paper considers generalizations of the completeness of the space and of the contractiveness of the mapping and shows that some recent extensions of Banach's theorem carry over to spaces whose topologies are generated by families of quasi-pseudometrics.
Fixed points of asymptotically regular multivalued mappings
Authors: Beg Ismat , Azam Akbar 
Published: April 2009

AbstractSome results on fixed point of asymptotically regular multivalued mapping are obtained in metric spaces. The structure of common fixed points and coincidence points of a pair of compatible multivalued mappings is also discussed. Our work generalizes known results of Aubin and Siegel, Dube, Dube and Singh, Hardy and Rogers, Hu, Iseki, Jungck, Kaneko, Nadler, Ray and Shiau, Tan and Wong.
Hypersurfaces of En+1 Satisfying Δx = Ax + B
Authors: Hasanis Th. , Vlachos Th. 
Published: April 2009

AbstractWe consider hypersurfaces of En+1 whose position vector x satisfies Δx = Ax + B, where Δ is the induced Laplacian, and prove that these are open parts of minimal hypersurfaces, hyperspheres or generalized circular cylinders.
On zero-sum turan problems of Bialostocki and Dierker
Authors: Caro Y. , Roditty Y. 
Published: April 2009

AbstractAssume G is a graph with m edges. By T(n, G) we denote the classical Turan number, namely, the maximum possible number of edges in a graph H on n vertices without a copy of G. Similarly if G is a family of graphs then H does not have a copy of any member of the family. A Zk-colouring of a graph G is a colouring of the edges of G by Zk, the additive group of integers modulo k, avoiding a copy of a given graph H, for which the sum of the values on its edges is 0 (mod k). By the Zero-Sum Turan number, denoted T(n, G, Zk), k¦m, we mean the maximum number of edges in a Zk-colouring of a graph on n vertices that contains no zero-sum (mod k) copy of G. Here we mainly solve two problems of Bialostocki and Dierker [6].Problem 1. Determine T(n, tK2, Zk) for ¦|t. In particular, is it true that T(n, tK2, Zk) = T(n, (t+k-1)K2)?Problem 2. Does there exist a constant c(t, k) such that T(n, Ft, Zk) ≦ c(t, k)n, where Ft is the family of cycles of length at least t?
The residual finiteness of HNN-extensions and generalized free products of nilpotent groups: a characterization
Authors: Raptis E. , Varsos D. 
Published: April 2009

AbstractWe study the residual finiteness of free products with amalgamations and HNN-extensions of finitely generated nilpotent groups. We give a characterization in terms of certain conditions satisfied by the associated subgroups. In particular the residual finiteness of these groups implies the possibility of extending the isomorphism of the associated subgroups to an isomorphism of their isolated closures in suitable overgroups of the factors (or the base group in case of HNN-extensions).
On the geometry of multisymplectic manifolds
Authors: Cantrijn F. , Ibort A. , De León M. 
Published: April 2009

AbstractA multisymplectic structure on a manifold is defined by a closed differential form with zero characteristic distribution. Starting from the linear case, some of the basic properties of multisymplectic structures are described. Various examples of multisymplectic manifolds are considered, and special attention is paid to the canonical multisymplectic structure living on a bundle of exterior k-forms on a manifold. For a class of multisymplectic manifolds admitting a ‘Lagrangian’ fibration, a general structure theorem is given which, in particular, leads to a classification of these manifolds in terms of a prescribed family of cohomology classes.
On the Stone-Čech bicompactification of a bispace
Authors: Garcia-Ferreira S. , Romaguera S. , Sanchis M. 
Published: April 2009

AbstractIn this paper we study the Stone-Čech bicompactification () of the bispace (X, P, Q). We show that the ring of all continuous real-valued functions on () may be identified with the uniform closure of a suitable subring ofC(). Using this result, we give a characterization of the Wallman-Sanin compactifications of the pairwise Tychonoff bitopological spaces.
Fractal n-hedral tilings of ℝd
Authors: Xu You 
Published: April 2009

AbstractAn n-hedral tiling of ℝd is a tiling with each tile congruent to one of the n distinct sets. In this paper, we use the iterated function systems (IFS) to generate n-hedral tilings of ℝd. Each tile in the tiling is similar to the attractor of the IFS. These tiles are fractals and their boundaries have the Hausdorff dimension less than d. Our results generalize a result of Bandt.
Landau-Lifshitz equation of ferromagnetism with external magnetic field
Authors: Pang P. Y. H. , Xiao J. , Zhou F. 
Published: April 2009

AbstractIn this article, we prove the existence and uniqueness of solution for the Cauchy problem of the Landau-Lifshitz equation of ferromagnetism with external magnetic field. We also show that the solution is globally regular with the exception of at most finitely many blow-up points. An energy identity at blow-up points is presented.
Pseudo MV-algebras are intervals in ℓ-groups
Authors: Dvurečenskij Anatolij 
Published: April 2009

AbstractWe show that any pseudo MV-algebra is isomorphic with an interval Γ(G, u), where G is an ℓ-group not necessarily Abelian with a strong unit u. In addition, we prove that the category of unital ℓ-groups is categorically equivalent with the category of pseudo MV-algebras. Since pseudo MV-algebras are a non-commutative generalization of MV-algebras, our assertions generalize a famous result of Mundici for a representation of MV-algebras by Abelian unital ℓ-groups. Our methods are completely different from those of Mundici. In addition, we show that any Archimedean pseudo MV-algebra is an MV-algebra.
Transcendental meromorphic solutions of some algebraic differential equations
Authors: Ishizaki Katsuya , Toda Nobushige 
Published: April 2009

AbstractIn this paper we treat transcendental meromorphic solutions of some algebraic differential equations. We consider the number of distinct transcendental meromorphic solutions. Algebraic relations between meromorphic solutions and comparisons of the growth of transcendental meromorphic solutions are also discussed.
Baer and quasi-Baer properties of group rings
Authors: Yi Zhong , Zhou Yiqiang 
Published: April 2009

AbstractA ring R is said to be a Baer (respectively, quasi-Baer) ring if the left annihilator of any nonempty subset (respectively, any ideal) of R is generated by an idempotent. It is first proved that for a ring R and a group G, if a group ring RG is (quasi-) Baer then so is R; if in addition G is finite then |G|–1 € R. Counter examples are then given to answer Hirano's question which asks whether the group ring RG is (quasi-) Baer if R is (quasi-) Baer and G is a finite group with |G|–1 € R. Further, efforts have been made towards answering the question of when the group ring RG of a finite group G is (quasi-) Baer, and various (quasi-) Baer group rings are identified. For the case where G is a group acting on R as automorphisms, some sufficient conditions are given for the fixed ring RG to be Baer.
On Cm-bounding sets
Authors: Biström Peter , Bjon Sten , Lindström Mikael 
Published: April 2009

AbstractLet E be a quasi-complete locally convex space and A a subset of E. It is shown that if every real-valued C∞-function in the weak topology of E is bounded on A, then A is relatively weakly compact. Furthermore, if all real-valued C∞-functions on E are bounded on A, then A is relatively compact in the associated semi-weak topology of E.