bluuebunny/crossref_metadata_2025 huggingface dataset:
S-cone signals invisible to the motion system can improve motion extraction via grouping by color
Authors: MARTINOVIC JASNA , MEYER GEORG , MÜLLER MATTHIAS M. , WUERGER SOPHIE M.
Published: April 2009

The purpose of this study was to test whether color–motion correlations carried by a pure color difference (S-cone component only) can be used to improve global motion extraction. We also examined the neural markers of color–motion correlation processing in event-related potentials. Color and motion information was dissociated using a two-colored random dot kinematogram, wherein coherent motion and motion noise differed from each other only in their S-cone component, with spatial and temporal parameters set so that global motion processing relied solely on a constant L-M component. Hence, when color and the local motion direction are correlated, more efficient segregation of coherent motion can only be brought about by the S-cone difference, and crucially, this S-cone component does not provide any effective input to a global motion mechanism but only changes the color appearance of the moving dots. The color contrasts (vector length in the Svs. L-M plane) of both the dots carrying coherent motion and the dots moving randomly were fixed at motion discrimination threshold to ensure equal effectiveness for motion extraction. In the behavioral experiment, participants were asked to discriminate between coherent and random motion, andd′ was determined for three different conditions: uncorrelated, uncued correlated, and cued correlated. In the electroencephalographic experiment, participants discriminated direction of motion for uncued correlated and cued correlated conditions. Color–motion correlations were found to improve performance. Cueing a specific color also modulated the N1 component of the event-related potential, with sources in visual area middle temporal. We conclude that S-cone signals “invisible” to the motion system can influence the analysis by direction-selective motion mechanisms through grouping of local motion signals by color. This grouping mechanism must precede motion processing and is likely to be under attentional control.
The Cuneiform Conception of Celestial Space and Time
Authors: Brown David
Published: April 2009

The significance to the modern world of Mesopotamian celestial divination and astronomy cannot be overstated. The names and the ‘ominous’ values assigned to the heavenly bodies by the Mesopotamians underlie Western astrology, and have also influenced Indian astrology. Many of the key features in the astronomy of Hipparchus and Ptolemy, which later passed into the astronomy of the medieval world, were borrowed from the astronomers of Babylon and Uruk. The zodiac, the Metonic cycle, horoscopy, and a variety of astrological techniques are all first attested in Mesopotamia. The same goes for units, notably those divisions of space and time which are now used throughout the world (such as 60 minutes in an hour and 360° in a circle) which can be traced back to cuneiform antecedents.
The Plancherel formula for the horocycle space and generalizations
Authors: Lipsman Ronald L.
Published: April 2009

The Plancherel formula for the horocycle space, and several generalizations, is derived within the framework of quasi-regular representations which have monomial spectrum. The proof uses only machinery from the Penney-Fujiwara distribution-theoretic technique; no special semisimple harmonic analysis is needed. The Plancherel formulas obtained include the spectral distributions and the intertwining operators that effect the direct integral decomposition of the quasi-regular representation.
Shadowing, expansiveness and hyperbolic homeomorphisms
Authors: Ombach Jerzy
Published: April 2009

The purpose of this paper is to complete results concerning the class ℋ of expansive homeomorphisms having the pseudo orbits tracing property on a compact metric space. We show that hyperbolic homeomorphisms introduced by Mañé in [8] are exactly those in the class ℋ then by the result of [12, 20] they form a class equal to the Smale space introduced by Ruelle in [18]. Next, assuming that the phase space is a smooth manifold, we show that a diffeomorphism is Anosov if and only if it is in the class ℋ and is a lower semi-continuity point of the map which assigns to any diffeomorphism the supremum of its expansive constants (possibly zero). Then we discuss the behavior of the dynamical systems generated by homeomorphisms from ℋ near their basic sets.
Weighted p-Sidon sets
Authors: Hare K. E. , Wilson D. C.
Published: April 2009

A weighted generalization of a p-Sidon set, called an (a, p)-Sidon set, is introduced and studied for infinite, non-abelian, connected, compact groups G. The entire dual object Ĝ is shown never to be central (p − 1, p)-Sidon for 1 ≦ p < 2, nor central (1 + ε, 2)-Sidon for ε > 0. Local (p, p)-Sidon sets are shown to be identical to local Sidon sets. Examples are constructed of infinite non-Sidon sets which are central (2p − 1, p)-Sidon, or (p − 1, p)-Sidon, for 1 < p < 2. Full m-fold FTR sets are proved not to be central (a, 2m/(m + 1))-Sidon for any a > 1.
Decomposing cubes
Authors: Horak P. , Širáň J. , Wallis W.
Published: April 2009

A graph H decomposes into a graph G if one can write H as an edge-disjoint union of graphs isomorphic to G. H decomposes into D, where D is a family of graphs, when H can be written as a union of graphs each isomorphic to some member of D, and every member of D is represented at least once. In this paper it is shown that the d-dimensional cube Qd decomposes into any graph G of size d each of whose blocks is either an even cycle or an edge. Furthennore, Qd decomposes into D, where D is any set of six trees of size d.
Odometer action on Riesz product
Authors: Yoshida Masamichi
Published: April 2009

We consider the Riesz product with a constant coefficient and odometer action over infinite product spaces. By studying the ratio set we can conclude the type of the above dynamical systems is III1.
Stability of production economies
Authors: Tan Kok-Keong , Yu Jian , Yuan Xian-Zhi
Published: April 2009

In this paper, the concept of essential equilibria for production economies is first given. We then prove that in ‘most’ production economies (in the sense of Baire category) all equilibria are essential.
Natural dualities for dihedral varieties
Authors: Davey B. A. , Quackenbush R. W.
Published: April 2009

A strong, natural duality is established for the variety by a dihedral gruop of order 2m with m odd. This is the first natural duality for a non-abelian variety of groups.
The modular group algebra problem for groups of orderp5
Authors: Salim Mohamed A. M. , Sandling Robert
Published: April 2009

We show thatp-groups of orderp5are determined by their group algebras over the field ofpelements. Many cases have been dealt with in earlier work of ourselves and others. The only case whose details remain to be given here is that of groups of nilpotency class 3 forpodd.
A transitive self-polar double-twenty of planes
Authors: Kirkpatrick P. B.
Published: April 2009

We demonstrate the existence, in the 5-dimensional projective space over any field J in which 1 + 1 ≠ 0 and −1 is a square, of a non-degenerate double-twenty of planes (ℋ, K) with the property that there is a group of collineations which acts transitively on ℋ ∪ K while each element of the group either maps ℋ onto itself and K onto itself or else swaps ℋ with K. If there is an involutory automorphism of J which swaps the two square roots of −1, then (ℋ, K) is also self-polar (with respect to a unitary polarity). We describe some of the geometry (in both 5-dimensional and 3-dimensional space) associated with the double-twenty (ℋ, K) and its group.
A new embedding scheme for groups and some applications
Authors: Obraztsov Viatcheslav N.
Published: April 2009

In this paper a scheme of an ‘economical’ embedding of an arbitrary set of groups without involutions in an infinite group with a proper simple normal subgroup is presented. This scheme is then applied to construction of groups with new properties.
Spectral and asymptotic properties of dominated operators
Authors: Räbiger Frank , Wolff Manfred P. H.
Published: April 2009

We investigate the relationship between the peripheral spectrum of a positive operator T on a Banach lattice E and the peripheral spectrum of the operators S dominated by T, that is, ]Sx] ≤ T]x] for all x ε E. This can be applied to obtain inheritance results for asymptotic properties of dominated operators.
Presentations of omega-categories by directed complexes
Authors: Crans Sjoerd E. , Steiner Richard
Published: April 2009

The theory of directed complexes is extended from free ω-categories by defining presentations in which the generators are atoms and the relations are equations between molecules. Our main result relates these presentations to the more standard algebraic presentations; we also show that every ω-category has a presentation by directed complexes. The approach is similar to that used by Crans for pasting presentations.
Maximal ideal space of function algebras
Authors: González Jorge Bustamante , Conde Raul Escobedo
Published: April 2009

We present a representation theory for the maximal ideal space of a real function algebra, endowed with the Gelfand topology, using the theory of uniform spaces. Application are given to algebras of differentiable functions in a normęd space, improving and generalizing some known results.
Modified cauchy kernels and functional calculus for operators on Banach space
Authors: Franks Edwin
Published: April 2009

In Banach space operators with a bounded H∞ functional calculus, Cowling et al. provide some necessary and sufficient conditions for a type-ω operator to have a bounded H∞ functional calculus. We provide an alternate development of some of their ideas using a modified Cauchy kernel which is L1 with respect to the measure ]dz]/]z]. The method is direct and has the advantage that no transforms of the functions are necessary.
Functions with unbounded ∂-derivative and their boundary functions
Authors: Zhiguo Chen , Jixiu Chen , Chengqi He
Published: April 2009

LetF(z)be a continuous complex-valued function defined on the closed upper half planeHwhose generalized derivative ∂F(z)is unbounded. In this paper, we discuss the relationship between the increasing order of ]∂F(x + iy)] wheny→ 0 and that of λf(x, t) ](F(x + t)− 2F(x)+F(x − t))/t], (x, t∈R), whent→ 0.
Maximal sublattices and Frattini sublattices of bounded lattices
Authors: Adams M. E. , Freese Ralph , Nation J. B. , Schmid Jürg
Published: April 2009

We investigate the number and size of the maximal sublattices of a finite lattice. For any positive integerk, there is a finite lattice L with more that ]L]ksublattices. On the other hand, there are arbitrary large finite lattices which contain a maximal sublattice with only 14 elements. It is shown that every bounded lattice is isomorphic to the Frattini sublattice (the intersection of all maximal sublattices) of a finite bounded lattice.
Stability with a general rate function for a class of stochastic evolution equations in infinite dimensional spaces
Authors: Liu Kai
Published: April 2009

The aim of this paper is to investigate the almost sure stability with a certain rate function λ(t) for a class of stochastic evolution equations in infinite dimensional spaces under various sufficient conditions. The results obtained here include exponential and polynomial stability as special cases. Much more refined sufficient conditions than the usual ones, for example, those described in [14], are obtained under our framework by the method of Liapunov functions. Two examples are given to illustrate our theory.
The Nachibin quasi-uniformity of a bi-Stonian space
Authors: Fletcher P. , Frith J. , Hunsaker W. , Schauerte A.
Published: April 2009

It is known that every frame is isomorphic to the generalized Gleason algebra of an essentially unique bi-Stonian space (X, σ, τ) in which σ is T0. Let (X, σ, τ) be as above. The specialization order ≤σ, of (X, σ) is τ × τ-closed. By Nachbin's Theorem there is exactly one quasi-uniformity U on X such that ∩U = ≤σ and J(U*) = τ. This quasi-uniformity is compatible with σ and is coarser than the Pervin quasi-uniformity U of (X, σ). Consequently, τ is coarser than the Skula topology of σ and coincides with the Skula topology if and only if U = P.
S and g*λ-functions on compact Lie groups
Authors: Blank Brian E. , Fan Dashan
Published: April 2009

We characterize the Hardy spaces Hp(G) of a compact Lie groupG by means of S-functions in analogy with the theorem of Fefferman-Stein for Rn. We also characterize Hp(G) by means of the -functions.
Quadratic Diophantine equations and two generator Möbius groups
Authors: Tan Eng-Chye , Tan Ser-Peow
Published: April 2009

In this paper, we study the set of rational μ in (−2, 2) for which the group Gu generated by is not free by using quadratic Diophantine equations of the form ax2 −by2 = ±1. We give a new set of accumulation points for rational values of μ in (−2, 2) for which Gμ is not free, thereby extending the results of Beardon where he showed that are accumulation points, where N is an integer which is not a perfect square. In particular, we exhibit an infinite set of accumulation points for μ between 1 and 2 including the point 1.
Bases for induced characters
Authors: Navarro Gabriel
Published: April 2009

If G is a finite solvable group, we show that Isaacs' theory on partial characters on Hall π-subgroups can be developed for the nilpotent injectors of G. Therefore, the irreducible characters of G are partitioned into blocks associated to some nilpotent subgroups of G.
Generalized regular variation of second order
Authors: de Haan Laurens , Stadtmüller Ulrich
Published: April 2009

Assume that for a measurable funcionfon (0, ∞) there exist a positive auxiliary functiona(t)and some γ ∈ R such that. Thenfis said to be of generalized regular variation. In order to control the asymptotic behaviour of certain estimators for distributions in extreme value theory we are led to study regular variation of second order, that is, we assume thatexists non-trivially with a second auxiliary function a1(t). We study the possible limit functions in this limit relation (defining generalized regular variation of second order) and their domains of attraction. Furthermore we give the corresponding relation for the inverse function of a monotonefwith the stated property. Finally, we present an Abel-Tauber theorem relating these functions and their Laplace transforms.
Diffeomorphisms with the shadowing property
Authors: Sakai Kazuhiro
Published: April 2009

It is proved that for every diffeomorphism f on a surface satisfying Axiom A, f is in the C2-interior of the set of all diffeoomorphisms having the shadowing property if and only if f satisfies the strong transversality condition.
Probabilistic convergence spaces
Authors: Richardson G. D. , Kent D. C.
Published: April 2009

A basic theory for probabilistic convergence spaces based on filter convergence is introduced. As in Florescu's previous theory of probabilistic convergence structures based on nets, one is able to assign a probability that a given filter converges to a given point. Various concepts and theorems pertaining to convergence spaces are extended to the realm of probabilistic convergence spaces, and illustrated by means of examples based on convergence in probability and convergence almost everywhere. Diagonal axioms due to Kowalsky and Fischer are also studied, first for convergence spaces and then in the setting of probabilistic convergence spaces.
An extension of the Fejér-Jackson inequality
Authors: Brown Gavin , Wang Kun-Yang
Published: April 2009

Best-possible results are established for positivity of the partial sums of Σ sin k θ (k + α)−1. In fact odd sums are positive for −1 ≤ α ≤ α0 = 2.1 …, while 2k terms are positive on the subinterval ]0, π − 2μ0π(4k +1)−1 [, μ0 = 0.8128 …. This is analagous to the Gasper extension of the Szegö-Rogosinski-Young inequality for cosine sums.
Further geometry of the mean curvature one-form and the normal plane field one-form on a foliated Riemannian manifold
Authors: Cairns Grant , Escobales Richard H.
Published: April 2009

For foliations on Riemannian manifolds, we develop elementary geometric and topological properties of the mean curvature one-form κ and the normal plane field one-form β. Through examples, we show that an important result of Kamber-Tondeur on κ is in general a best possible result. But we demonstrate that their bundle-like hypothesis can be relaxed somewhat in codimension 2. We study the structure of umbilic foliations in this more general context and in our final section establish some analogous results for flows.
Generalised spectral analysis of fractional random fields
Authors: Anh V. V. , Lunney K. E.
Published: April 2009

This paper considers a large class of non-stationary random fields which have fractal characteristics and may exhibit long-range dependence. Its motivation comes from a Lipschitz-Holder-type condition in the spectral domain.

The paper develops a spectral theory for the random fields, including a spectral decomposition, a covariance representation and a fractal index. From the covariance representation, the covariance function and spectral density of these fields are defined. These concepts are useful in multiscaling analysis of random fields with long-range dependence.
Asymptotic behaviour of non-autonomous dissipative systems in Hilbert space
Authors: Guozhu Song
Published: April 2009

In this paper we discuss the asymptotic behaviour, as t → ∞, of the integral solution u(t) of the non-linear evolution equation where {A(t)}t≥0 is a family of m-dissipative operators in a Hilbert space H, and g ∈ Lloc (0, ∞ H).We give some sufficient conditions and some sufficient and necessary conditions to ensure that are weakly convergent.
The inner and outer space of 2-dimensional Laguerre planes
Authors: Polster B. , Steinke G. F.
Published: April 2009

The classical 2-dimensional Laguerre plane is obtained as the geometry of non-trivial plane sections of a cylinder in R3 with a circle in R2 as base. Points and lines in R3 define subsets of the circle set of this geometry via the affine non-vertical planes that contain them. Furthemore, vertical lines and planes define partitions of the circle set via the points and affine non-vertical lines, respectively, contained in them.

We investigate abstract counterparts of such sets of circles and partitions in arbitrary 2-dimensional Laguerre planes. We also prove a number of related results for generalized quadrangles associated with 2-dimensional Laguerre planes.
Integer points on algebraic curves with exceptional units
Authors: Poulakis Dimitrios
Published: April 2009

Let F(X, Y) be an absolutely irreducible polynomial with coefficients in an algebraic number field K. Denote by C the algebraic curve defined by the equation F(X, Y) = 0 and by K[C] the ring of regular functions on Cover K. Assume that there is a unit ϕ in K[C] − K such that 1 − ϕ is also a unit. Then we establish an explicit upper bound for the size of integral solutions of the equation F(X, Y) = 0, defined over K. Using this result we establish improved explicit upper bounds on the size of integral solutions to the equations defining non-singular affine curves of genus zero, with at least three points at ‘infinity’, the elliptic equations and a class of equations containing the Thue curves.
Generic continuity of minimal set-valued mappings
Authors: Moors W. B. , Giles J. R.
Published: April 2009

We study classes of Banach spaces where every set-valued mapping from a complete metric space into subsets of the Banach space which satisfies certain minimal properties, is single-valued and norm upper semi-continuous at the points of a dense Gδ subset of its domain. Characterisations of these classes are developed and permanence properties are established. Sufficiency conditions for membership of these classes are defined in terms of fragmentability and σ-fragmentability of the weak topology. A characterisation of non membership is used to show that l∞ (N) is not a member of our classe of generic continuity spaces.
Bifurcation at infinity for equations in spaces of vector-valued functions
Authors: Diamond P. , Kloeden P. E. , Krasnosel'skii A. M. , Pokrovskii A. V.
Published: April 2009

New existence conditions, under which an index at infinity can be calculated, are given for bifurcations at infinity of asymptotically linear equations in spaces of vector-valued functions. The case where a bounded nonlinearity has discontinuous principal homogeneous part is considered. The results are applied to 2π-periodic problems for two-dimensional systems of ordinary differential equations and to a vector two-point boundary value problem.
Pascal's triangles in Abelian and hyperbolic groups
Authors: Shapiro Michael
Published: April 2009

Given a group G and a finite generating set G, we take pG: G → Z to be the function which counts the number of geodesics for each group element g. This generalizes Pascal's triangle. We compute pG for word hyperbolic and describe generic behaviour in abelian groups.
Equivariant holomorphic maps into the Siegel disc and the metaplectic representation
Authors: Clerc Jean-Louis
Published: April 2009

We restrict the metaplectic representation to subgroupsGof the symplectic group associated to equivariant holomorphic maps into the Siegel disc. We describe the invariant subspaces of the decomposition, and reduce the problem to the decomposition of a space of ‘harmonic’ polynomials under the action of the maximal compact subgroup ofG.
A note on metric inhomogeneous Diophantine approximation
Authors: Dodson M. M.
Published: April 2009

An inhomogeneous version of a general form of the Jarník-Besicovitch Theorem is proved.
The product of independent random variables with slowly varying truncated moments
Authors: Shimura Takaaki
Published: April 2009

The Mellin-Stieltjes convolution and related decomposition of distributions in M(α) (the class of distributions μ on (0, ∞) with slowly varying αth truncated moments ) are investigated. Maller shows that if X and Y are independent non-negative random variables with distributions μ and v, respectively, and both μ and v are in D2, the domain attraction of Gaussian distribution, then the distribution of the product XY (that is, the Mellin-Stieltjes convolution μ ^ v of μ and v) also belongs to it. He conjectures that, conversely, if μ ∘ v belongs to D2, then both μ and v are in it. It is shown that this conjecture is not true: there exist distributions μ ∈ D2 and v μ ∈ D2 such that μ ^ v belongs to D2. Some subclasses of D2 are given with the property that if μ ^ v belongs to it, then both μ and v are in D2.
Inverse semigroups with zero: covers and their structure
Authors: Bulman-Fleming Sydney , Fountain John , Gould Victoria
Published: April 2009

We obtain analogues, in the setting of semigroups with zero, of McAlister's convering theoren and the structure theorems of McAlister, O'Carroll, and Margolis and Pin. The covers come from a classCof semigroups defined by modifying one of the many characterisations ofE-unitary inverse semigroups, namely, that an inverse semigroups isE-unitary if and only if it is an inverse image of an idempotent-pure homomorphism onto a group. The classCis properly contained in the class of allE*-unitary inverse semigroups introduced by Szendrei but properly contains the class of strongly categoricalE*-unitary semigroups recently considered by Gomes and Howie.
On the linear prediction of some Lp random fields
Authors: Cheng R. , Houdré C.
Published: April 2009

This work is concerned with the prediction problem for a class of Lp-random fields. For this class of fields, we derive prediction error formulas, spectral factorizations, and orthogonal decompositions.
Notes on Erdös-Turán inequality
Authors: Ohkubo Yukio
Published: April 2009

A new version of Erdös-Turán's inequality is described. The purpose of the present paper is to show that the inequality provides better upper bounds for the discrepancies of some sequences than usual Erdös-Turán's inequality.
A family of strongly singular operators
Authors: Folch-Gabayet Magali
Published: April 2009

Let ψ be a positive function defined near the origin such lim1 →0+ ψ(t) = 0. We consider the operator Tzƒ, defined as the pricipal value of the convolution of function ƒ and a kernel K(t) = eiy(t)t−z /ψ(t)1−z, where z is a complex number, 0 ≤ Re(z) ≤ 1, 0 < t ≤ 1 and γ is a real function. Assuming certain regularity conditions on ψ and γ and certain relations between ψ and γ we show that Tθ is a bounded operator on Lp (R) for 1/p = (1+ θ) /2 and 0 ≤ θ < 1, and T1 is bounded from H1 (R) to L1 (R).
Congruence intersection properties for varieties of algebras
Authors: Agliano Paolo , Baker Kirby A.
Published: April 2009

It is shown that a variety ν has distributive congruence lattices if and only if the intersection of two principal congruence relations is definable by equations involving terms with parameters. The nature of the terms involved then provides a useful classification of congruence distributive varieties. In particular, the classification puts into proper perspective two stronger properties. A variety is said to have the Principal Intersection Property if the intersection of any two principal congruence relations is principal, or the Compact Intersection Property if the intersection of two compact congruence relations is compact. For non-congruence-distributive varieties, it is shown that some useful constuctions are nevertheless possible.
A classification scheme for nonoscilatory solutions of a higher order neutral nonlinear difference equation
Authors: Wan-Tong Li , Cheng Sui Sun , Zhang Guang
Published: April 2009

Nonoscillatory solutions of a nonlinear neutral type higher order difference equations are classified by means of their asymptotic behaviors. Existence criteria are then provided for justification of such classficiation.
Amenability and semisimplicity for second duals of quotients of the Fourier algebraA(G)
Authors: Granirer Edmond E.
Published: April 2009

LetF ⊂ Gbe closed andA(F) = A(G)/IF. IfFis a Helson set thenA(F)**is an amenable (semisimple) Banach algebra. Our main result implies the following theorem: LetGbe a locally compact group,F ⊂ Gclosed,a ∈ G. Assume either (a) For some non-discrete closed subgroupH, the interior ofF ∩ aHinaHis non-empty, or (b)R ⊂ G, S ⊂ Ris a symmetric set andaS ⊂ F. ThenA(F)**is a non-amenable non-semisimple Banach algebra. This raises the question: How ‘thin’ canFbe forA(F)**to remain a non-amenable Banach algebra?
Cesàro kernels on classical groups
Authors: Fan Dashan
Published: April 2009

We study the Cesàro operator on the classical group G and give a necessary and sufficient condition on the index α = α(G) for which the operator is convergent to f(U) for any continuous function f as N → ∞. The result in this paper solves a question posed by Gong in the book Harmonic analysis on classical groups.
On a conjecture of Crittenden and Vanden Eynden concerning coverings by arithmetic progressions
Authors: Simpson R. J.
Published: April 2009

Crittenden and Vanden Eynden conjectured that ifnarithmetic progressions, each having modulus at leastk, include all the integers from 1 tok2n-k+1, then they include all the integers. They proved this for the casesk= 1 andk= 2. We give various necessary conditions for a counterexample to the conjecture; in particular we show that if a counterexample exists for some value ofk, then one exists for thatkand a value ofnless than an explicit function ofk.
Mixed cusp forms and parabolic cohomology
Authors: Lee Min Ho
Published: April 2009

Let Sk, l(Γ, ω, χ) be the space of mixed cusp forms of type (k, l) associated to a Fuchsian group Γ, a holomorphic map ω: ℋ → ℋ of the upper half plane into itself and a homomorphism χ: Γ → SL(2, R) such that ω and χ are equivariant. We construct a map from Sk, l(Γ, ω, χ) to the parabolic cohomology space of Γ with coefficients in some Γ-module and prove that this map is injective.
The Dehn function and a regular set of normal forms for R. Thompson's group F
Authors: Guba V. S. , Sapir M. V.
Published: April 2009

We show that the group F discovered by Richard Thompson in 1965 has a subexponential upper bound for its Dehn function. This disproves a conjecture by Gersten. We also prove that F has a regular terminating confluent presentation.
Effective measures of irrationality for certain algebraic numbers
Authors: Bennett Michael A.
Published: April 2009

In this paper, we derive a number of explicit lower bounds for rational approximation to certain cubic irrationalities, proving, for example, that for any non-zero integers p and q. A number of these irrationality measures improve known results, including those for . Some Diophantine consequences are briefly discussed.
Two-term Edgeworth expansion for M-estimators of a linear regression parameter without Cramér-type conditions and an application to the bootstrap
Authors: Karabulut I. , Lahiri S. N.
Published: April 2009

A two-term Edgeworth expansion for the distribution of an M-estimator of a simple linear regression parameter is obtained without assuming any Cramér-type conditions. As an application, it is shown that certain modification of the naive bootstrap procedure is second order correct even when the error variables have a lattice distribution. This is in marked contrast with the results of Singh on the sample mean of independent and identically distributed random variables.
Value distribution of certain monomials of algebroid functions
Authors: Katajamäki Kari
Published: April 2009

Hayman has shown that iffis a transcendental meromorphic function andn≽ 3, thenfnf′ assumes all finite values except possibly zero infinitely often. We extend his result in three directions by considering an algebroid function ω, its monomial ωn0ω′n1, and by estimating the growth of the number of α-points of the monomial.
Free Lie algebras as modules for symmetric groups
Authors: Bryant R. M. , Kovács L. G. , Stöhr Ralph
Published: April 2009

Let r be a positive integer, F a field of odd prime characteristic p, and L the free Lie algebra of rank r over F. Consider L a module for the symmetric group , of all permutations of a free generating set of L. The homogeneous components Ln of L are finite dimensional submodules, and L is their direct sum. For p ≤ r ≤ 2p, the main results of this paper identify the non-porojective indecomposable direct summands of the Ln as Specht modules or dual Specht modules corresponding to certain partitions. For the case r = p, the multiplicities of these indecomposables in the direct decompositions of the Ln are also determined, as are the multiplicities of the projective indecomposables. (Corresponding results for p = 2 have been obtained elsewhere.)
Some thin Lie algebras related to Albert-Frank algebras and algebras of maximal class
Authors: Caranti A. , Mattarei S.
Published: April 2009

We investigate a class of infinite-dimensional, modular, graded Lie algebra in which the homogeneous components have dimension at most two. A subclass of these algebras can be obtained via a twisted loop algebra construction from certain finite-dimensional, simple Lie algebras of Albert-Frank type.

Another subclass of these algebras is strictly related to certain graded Lie algebras of maximal class, and exhibits a wide range of behaviours.
Enumerating p-Groups
Authors: Eick Bettina , O'Brien E. A.
Published: April 2009

We present a new algorithm which uses a cohomological approach to determine the groups of order pn, where p is a prime. We develop two methods to enumerate p-groups using the Cauchy-Frobenius Lemma. As an application we show that there are 10 494213 groups of order 29.

1991 Mathematics subject classification (Amer. Math. Soc.): primary 20D15.
A recognition algorithm for non-generic classical groups over finite fields
Authors: Niemeyer Azice C. , Praeger Cheryl E.
Published: April 2009

In a previous paper the authors described an algorithm to determine whether a group of matrices over a finite field, generated by a given set of matrices, contains one of the classical groups or the special linear group. The algorithm was designed to work for all sufficiently large field sizes and dimensions of the matrix group. However, it did not apply to certain small cases. Here we present an algorithm to handle the remaining cases. The theoretical background of the algorithm presented in this paper is a substantial extension of that needed for the original algorithm.
Bounds in the restricted Burnside problem
Authors: Vaughan-Lee Michael , Zel'manov E. I.
Published: April 2009

We survey the current state of knowledge of bounds in the restricted Burnside problem. We make two conjectures which are related to the theory of PI-algebras.
Posets and differential graded algebras
Authors: Ramagge Jacqui , Wheeler Wayne W.
Published: April 2009

If P is a partially ordered set and R is a commutative ring, then a certain differential graded R-algebra A•(P) is defined from the order relation on P. The algebra A•() corresponding to the empty poset is always contained in A•(P) so that A•(P) can be regarded as an A•()-algebra. The main result of this paper shows that if R is an integral domain and P and P′ are finite posets such that A•(P)≅A•(P′) as differential graded A•()-algebras, then P and P′ are isomorphic.
Lp–Lrestimates for the Poisson semigroup on homogeneous trees
Authors: Setti Alberto G.
Published: April 2009

Let be a homogeneous tree of degree at least three. In this paper we investigate for which values of p and r the (σθ)-Poisson semigroup is Lp – Lr,-bounded, and we sharp estimate for the corresponding operator norms.
A family of dominant Fitting classes of finite soluble groups
Authors: Ballester-Bolinches A. , Martínez-Pastor A. , Pérez-Ramos M. D.
Published: April 2009

In this paper a large family of dominant Fitting classes of finite soluble groups and the description of the corresponding injectors are obtained. Classical constructions of nilpotent and Lockett injectors as well as p-nilpotent injectors arise as particular cases.
Truncated tetrahedra and their reflection groups
Authors: Marshall T. H.
Published: April 2009

We outline the classification, up to isometry, of all tetrahedra in hyperbolic space with one or more vertices truncated, for which the dihedral angles along the edges formed by the truncations are all π/2, and those remaining are all submultiples of π. We show how to find the volumes of these polyhedra, and find presentations and small generating sets for the orientation-preserving subgroups of their reflection groups.

For particular families of these groups, we find low index torsion free subgroups, and construct associated manifolds and manifolds with boundary. In particular, for each g ≥ 2, we find a sequence of hyperbolic manifolds with totally geodesic boundary of genus g, which we conjecture to be of least volume among such manifolds.
Finite groups that need more generators than any proper quotient
Authors: Volta Francesca Dalla , Lucchini Andrea
Published: April 2009

A structure theorem is proved for finite groups with the property that, for some integer m with m ≥ 2, every proper quotient group can be generated by m elements but the group itself cannot.
A note on Engel groups and local nilpotence
Authors: Burns R. G. , Medvedev Yuri
Published: April 2009

This paper is concerned with the question of whether n-Engel groups are locally nilpotent. Although this seems unlikely in general, it is shown here that it is the case for the groups in a large class C including all residually soluble and residually finite groups (in fact all groups considered in traditional textbooks on group theory). This follows from the main result that there exist integers c(n), e(n) depending only on n, such that every finitely generated n-Engel group in the class C is both finite-of-exponent-e(n)–by–nilpotent-of-class≤c(n) and nilpotent-of-class≤c(n)–by–finite-of-exponent-e(n). Crucial in the proof is the fact that a finitely generated Engel group has finitely generated commutator subgroup.
Crossed products of Hilbert C*-bimodules by bundles
Authors: Kajiwara Tsuyoshi , Watatani Yasuo
Published: April 2009

We present the definition of crossed products of Hilbert C*-bimodules by Hilbert bundles with commuting finite group actions and finite dimensional fibers. This is a general construction containing the bundle construction and crossed products of Hilbert C*-bimodule by finite groups. We also study the structure of endomorphism algebras of the tensor products of bimodules. We also define the multiple crossed products using three bimodules containing more than 2 bundles and show the associativity law. Moreover, we present some examples of crossed product bimodules easily computed by our method.
Compact Toeplitz operators on weighted harmonic Bergman spaces
Authors: Stroethoff Karel
Published: April 2009

We consider the Bergman spaces consisting of harmonic functions on the unit ball in Rn that are squareintegrable with respect to radial weights. We will describe compactness for certain classes of Toeplitz operators on these harmonic Bergman spaces.
Contracting spacelike hypersurfaces by their inverse mean curvature
Authors: Holder Michael
Published: April 2009

In this work we study the behaviour of compact, smooth, orientable, spacelike hypersurfaces without boundary, which are immersed in cosmological spacetimes and move under the inverse mean curvature flow. We prove longtime existence and regularity of a solution to the corresponding nonlinear parabolic system of partial differential equations.
Apéry sequences and legendre transforms
Authors: Jin Yuan , Dickinson H.
Published: April 2009

A lower bound for the minimal length of the polynomial recurrence of a binomial sum is obtained.
The arithmetic of a semigroup of series of Walsh functions
Authors: Il'inskaya I. P.
Published: April 2009

Let be the classical system of the Walsh functions, the multiplicative semigroup of the functions represented by series of functions Wk(t)with non-negative coefficients which sum equals 1. We study the arithmetic of . The analogues of the well-known [ related to the arithmetic of the convolution semigroup of probability measures on the real line are valid in . The classes of idempotent elements, of infinitely divisible elements, of elements without indecomposable factors, and of elements without indecomposable and non-degenerate idempotent factors are completely described. We study also the class of indecomposable elements. Our method is based on the following fact: is isomorphic to the semigroup of probability measures on the groups of characters of the Cantor-Walsh group.
Hyperbolic knot complements without closed embedded totally geodesic surfaces
Authors: Ichihara Kazuhiro , Ozawa Makoto
Published: April 2009

It is conjectured that a hyperbolic knot complement does not contain a closed embedded totally geodesic surface. In this paper, we show that there are no such surfaces in the complements of hyperbolic 3-bridge knots and double torus knots. Some topological criteria for a closed essential surface failing to be totally geodesic are given. Roughly speaking, sufficiently ‘complicated’ surfaces cannot be totally geodesic.
A remark on robustness and weak continuity of M-estimators
Authors: Clarke Brenton R.
Published: April 2009

Global weak continuity of M-functionals in a neighbourhood of the parametric distribution is established. This has implications for robustness of M-estimators vis a vis definitions put forward by Hampel. For instance the Tukey bisquare location estimator is robust on neighbourhoods of the parametric model, but the median is not.
A Generalization of the Schwarz Lemma to Normal Selfaps of Complex Spaces
Authors: Joseph James E. , Kwack Myung H.
Published: April 2009

We establish generalizations for normal selfmaps of complex spaces of the Schwarz lemma and of recent results on convergence of iterates of holomorphic selfmaps of taut spaces.
Asymptotic Behaviour of Continuous Time and State Branching Processes
Authors: Li Zeng-Hu
Published: April 2009

We prove some limit theorems for contiunous time and state branching processes. The non-degenerate limit laws are obtained in critical and non-critical cases by conditioning or introducing immigration processes. The limit laws in non-critical cases are characterized in terms of the cononical measure of the cumulant semigroup. The proofs are based on estimates of the cumulant semigroup derived from the forward and backward equations, which are easier than the proffs in the classical setting.
Hahn-Banach Type Theorems for Locally Convex Cones
Authors: Roth Walter
Published: April 2009

We prove Hahn-Banach type theorems for linear functionals with values in R∪{+∞} on ordered cones, Using the concept of locally convex cones, we provide a sandwich theorem involving sub- and superlinear functionals which are allowed to attain infinite values. It render general versions of well-known extension and separation results. We describe the range of all linear functionals sandwiched between given sub- and superlinear functionals on an ordered cone. The results are of interest even in vector spaces, since we consider sublinear functionals that may attain the value +∞.
On Symmetric Quasicircles
Authors: Wu Shengjian , Yang Shanshuang
Published: April 2009

We study an important subclass of quasicircles, namely, symmetric quasicircles. Several characterizations for quasicircles, such as the reverse triangle inequality, the M -condition and the quasiconformal extension property, have been extended to symmetric quasicircles by Becker and Pommerenke and by Gardiner and Sullivan. In this paper we establish several relations among various domain constants such as quasiextremal distance constants, (local) reflection constants and (local) extension constants for this class. We also give several characterizations for symmetric quasicircles such as the strong quadrilateral inequality and the strong extremal distance property. They correspond to the quadrilateral inequality and the extremal distance property for quasicircles.
Euler Characteristics and imbeddings of hyperbolic Coxeter groups
Authors: Maxwell George
Published: April 2009

This paper has a twofold purpose. The first is to compute the Euler characteristics of hyperbolic Coxeter groups Ws of level 1 or 2 by a mixture of theoretical and computer aided methods. For groups of level 1 and odd values of |S|, the Euler characteristic is related to the volume of the fundamental region of Ws in hyperbolic space. Secondly we note two methods of imbedding such groups in each other. This reduces the amount of computation needed to determine the Euler characteristics and also reduces the number of essentially different hyperbolic groups that need to be considered.
On certain pairs of automorphisms of rings, II
Authors: Brešar Matej
Published: April 2009

Let R be a prime ring of characteristic not 2. Automorphisms α and β of R satisfying α ≠ β, α ≠ β−1, and α + α−1 = β + β-1 are characterized. This result is an algebraic analogue of some results for operator algebras.
Some properties of quasiuniform multifunction spaces
Authors: Cao Jiling , Reilly Ivan L. , Romaguera Salvador
Published: April 2009

The aim of this paper is to explore some properties of quasiuniform multifunction spaces. Various kinds of completeness of the quasiuniform multifunction space (YmX, UmX) are characterized in terms of suitable properties of the range space (Y, U). We also discuss the local compactness of quasiuniform multifunction spaces. By using the notion of small-set symmetry, the classic result of Hunsaker and Naimpally is extended to the quasiuniform setting.
The singular ideal and radicals
Authors: Ferrero Miguel , Puczyłowski Edmund R.
Published: April 2009

Some properties of the singular ideal are established. In particular its behaviour when passing to one-sided ideals is studied. Obtained results are applied to study some radicals related to the singular ideal. In particular a radical S such that for every ring R, S(R) and R/S(R) are close to being a singular ring and a non-singular ring, respectively, is constructed.
T-regular probabilistic convergence spaces
Authors: Minkler J. , Minkler G. , Richardson G.
Published: April 2009

A probabilistic convergence structure assigns a probability that a given filter converges to a given element of the space. The role of the t-norm (triangle norm) in the study of regularity of probabilistic convergence spaces is investigated. Given a probabilistic convergence space, there exists a finest T-regular space which is coarser than the given space, and is referred to as the ‘T-regular modification’. Moreover, for each probabilistic convergence space, there is a sequence of spaces, indexed by nonnegative ordinals, whose first term is the given space and whose last term is its T-regular modification. The T-regular modification is illustrated in the example involving ‘convergence with probability λ’ for several t-norms. Suitable function space structures in terms of a given t-norm are also considered.
Rybakov's theorem in Fréchet spaces and completeness of L1-spaces
Authors: Ricker W. J.
Published: April 2009

We provide a simple and direct proof of the completeness of the L1-space of any vector measure taking its values in the class of Fréchet spaces which do not contain a copy of the sequence space ω.
Ergodicity and differences of functions on semigroups
Authors: Basit Bolis , Pryde A. J.
Published: April 2009

Iseki [11] defined a general notion of ergodicity suitable for functions ϕ: J → X where J is an arbitrary abelian semigroup and X is a Banach space. In this paper we develop the theory of such functions, showing in particular that it fits the general framework established by Eberlein [9] for ergodicity of semigroups of operators acting on X. Moreover, let A be a translation invariant closed subspace of the space of all bounded functions from J to X. We prove that if A contains the constant functions and ϕ is an ergodic function whose differences lie in A then ϕ ∈ A. This result has applications to spaces of sequences facilitating new proofs of theorems of Gelfand and Katznelson-Tzafriri [12]. We also obtain a decomposition for the space of ergodic vectors of a representation T: J → L(X) generalizing results known for the case J = Z+. Finally, when J is a subsemigroup of a locally compact abelian group G, we compare the Iseki integrals with the better known Cesàro integrals.
Difference equations in abstract spaces
Authors: Agarwal Ravi P. , O'Regan Donal
Published: April 2009

Existence results are presented for second order discrete boundary value problems in abstract spaces. Our analysis uses only Sadovskii's fixed point theorem.
Independance algebrique des derivees d'une periode du module de Carlitz
Authors: Denis Laurent
Published: April 2009

We prove here that thep- 1 first derivatives of the fundamental period of the Carliz module are algebraically independent. For that purpose we will show to use Mahler's method in this situtaion.
Compactness properties for perturbed semigroups and application to transport equation
Authors: Latrach Khalid
Published: April 2009

Using the comparsion results for positive compact operators by Aliprantis and Burkinshow, Mokhtar Kharroubi investigated cimpactness properties of positive semigroups on Banach latttices. The aim of this paper is to study these properties in general Banach spaces (without positivity). Our results generalize a part fo those obtained by Mokhtar-Kharroubi to general Banach spaces context. More specifically, we derive conditions which ensure the compactness of the remainder term Rn(t) for some inteter n. The improvement here is that it can applied directly to the neutron transport equation for a wide class of collision operators.
Weighted composition operators in weighted Banach spaces of analytic functions
Authors: Contreras M. D. , Hernandez-Diaz A. G.
Published: April 2009

We characterize the boundedness and compactness of weighted composition operators between weighted Banach spaces of analytic functionsand. we estimate the essential norm of a weighted composition operator and compute it for those Banach spaceswhich are isomorphic toc0. We also show that, when such an operator is not compact, it is an isomorphism on a subspace isomorphic toc0orl∞. Finally, we apply these results to study composition operators between Bloch type spaces and little Bloch type spaces.