bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soluble groups isomorphic to their non-nilpotent subgroups
Authors: Smith Howard , Wiegold James 
Published: April 2009

AbstractA group G belongs to the class W if G has non-nilpotent proper subgroups and is isomorphic to all of them. The main objects of study are the soluble groups in W that are not finitely generated. It is proved that there are no torsion-free groups of this sort, and a reasonable classification is given in the finite rank case.
On the homotopy type of the p-subgroup complex for finite solvable groups
Authors: Pulkus Jürgen , Welker Volkmar 
Published: April 2009

AbstractWe provide a wedge decomposition of the homotopy type of the p-subgroup complex in the case of a finite solvable group G. In particular, this includes a new proof of the result of Quillen which says that this complex is contractible if and only if there is a non-trivial normal p-subgroup in G. We also provide reduction formulas for the G-module structure of the homology groups. Our results are obtained with diagram-methods by gluing the p-subgroup complex of G along the p-subgroup complex of = G/N for a normal p′-subgroup of G.
The bounded vector measure associated to a conical measure and pettis differentiability
Authors: Rodriguez-Piazza L. , Romero-Moreno M. C. 
Published: April 2009

AbstractLet X be a locally convex space. Kluvánek associated to each X-valued countably additive vector measure a conical measure on X; this can also be done for finitely additive bounded vector measures. We prove that every conical measure u on X, whose associated zonoform Ku is contained in X, is associated to a bounded additive vector measure σ(u) defined on X, and satisfying σ(u)(H) ∈ H, for every finite intersection H of closed half-spaces. When X is a complete weak space, we prove that σ(u) is countably additive. This allows us to recover two results of Kluvánek: for any X, every conical measure u on it with Ku ⊆ X is associated to a countably additive X-valued vector measure; and every conical measure on a complete weak space is localizable. When X is a Banach space, we prove that σ(u) is countably additive if and only if u is the conical measure associated to a Pettis differentiable vector measure.
m-Wielandt series in infinite groups
Authors: Franchi Clara 
Published: April 2009

AbstractIn a group G, um (G) denotes the subgroup of the elements which normalize every subnormal subgroup of G with defect at most m. The m-Wielandt series of G is then defined in a natural way. G is said to have finite m-Wielandt length if it coincides with a term of its m-Wielandt series. We investigate the structure of infinite groups with finite m-Wielandt length.
On real forms of a complex algebraic curve
Authors: Bujalance E. , Gromadzki G. , Izquierdo M. 
Published: April 2009

AbstractTwo projective nonsingular complex algebraic curves X and Y defined over the field R of real numbers can be isomorphic while their sets X(R) and Y(R) of R-rational points could be even non homeomorphic. This leads to the count of the number of real forms of a complex algebraic curve X, that is, those nonisomorphic real algebraic curves whose complexifications are isomorphic to X. In this paper we compute, as a function of genus, the maximum number of such real forms that a complex algebraic curve admits.
Double circulant constructions of the Leech lattice
Authors: Chapman Robin 
Published: April 2009

AbstractWe consider the problem of finding, for each even number m, a basis of orthogonal vectors of length in the Leech lattice. We give such a construction by means of double circulant codes whenever m = 2p and p is a prime not equal to 11. From this one can derive a construction for all even m not of the form 2· 11r.
Sums of squares of integral linear forms
Authors: Sasaki Hideyo 
Published: April 2009

AbstractIn this paper we prove that every positive definite n-ary integral quadratic form with 12 < n < 13 (respectively 14 ≦ n ≤ 20) that can be represented by a sum of squares of integral linear forms is represented by a sum of 2 · 3n + n + 6 (respectively 3 · 4n + n + 3) squares. We also prove that every positive definite 7-ary integral quadratic form that can be represented by a sum of squares is represented by a sum of 25 squares.
The structure of finite groups in which permutability is a transitive relation
Authors: Robinson Derek J. S. 
Published: April 2009

AbstractThe structure of finite groups in which permutability is transitive (PT-groups) is studied in detail. In particular a finitePT-group has simple chief factors and thep-chief factors fall into at most two isomorphism classes. The structure of finiteT-groups, that is, groups in which normality is transitive, is also discussed, as is that of groups generated by subnormal or normalPT-subgroups.
Last passage times of minimum contrast estimators
Authors: Bose Arup , Chatterjee Snigdhansu 
Published: April 2009

AbstractWe study the last passage time and its asymptotic distribution for minimum contrast estimators defined through the minimization of a convex criterion function based on U-functionals. This includes cases of non-smooth estimators for vector valued parameters. We also derive a Bahadur-type representation and the law of iterated logarithms for such estimators.
On (2, 3, 7)-generation of maximal parabolic subgroups
Authors: Martino L. Di , Tamburini M. C. 
Published: April 2009

AbstractLet R be a ring with 1 and En (R) be the subgroup of GLn(R) generated by the matrices I + reij, r ∈ R, i ≠ j. We prove that the subgroup of consisting of the matrices of shape , where and , is (2, 3, 7)-generated whenever R is finitely generated and n, are large enough.
Automorphisms of Cayley graphs of metacyclic groups of prime-power order
Authors: Li Caiheng , Sim Hyo-Seob 
Published: April 2009

AbstractThis paper inverstigates the automorphism groups of Cayley graphs of metracyclicp-gorups. A characterization is given of the automorphism groups of Cayley grahs of a metacyclicp-group for odd primep. In particular, a complete determiniation of the automophism group of a connected Cayley graph with valency less than 2pof a nonabelian metacyclicp-group is obtained as a consequence. In subsequent work, the result of this paper has been applied to solve several problems in graph theory.
Ensuring commutativity of finite groups
Authors: Neumann B. H. 
Published: April 2009

AbstractComments are made on the following question. Let m, n be positive integers and g a finite group. Suppose that for all choices of a subset of cardinality m and of a subset of cardinality n in g some member of the first commutes with some member of the second. Under what conditions on m, n is the group abelian?
On the geometry of Lp (μ) with applications to infinite variance processes
Authors: Cheng R. , Miamee A. G. , Pourahmadi M. 
Published: April 2009

AbstractSome geometric properties of Lp spaces are studied which shed light on the prediction of infinite variance processes. In particular, a Pythagorean theorem for Lp is derived. Improved growth rates for the moving average parameters are obtained.
An integral formula for compact hypersurfaces in space forms and its applications
Authors: Alías Luis J. 
Published: April 2009

AbstractIn this paper we establish an integral formula for compact hypersurfaces in non-flat space forms, and apply it to derive some interesting applications. In particular, we obtain a characterization of geodesic spheres in terms of a relationship between the scalar curvature of the hypersurface and the size of its Gauss map image. We also derive an inequality involving the average scalar curvature of the hypersurface and the radius of a geodesic ball in the ambient space containing the hypersurface, characterizing the geodesic spheres as those for which equality holds.
A decomposition theorem for homogeneous algebras
Authors: Sweet L. G. , Macdougall J. A. 
Published: April 2009

AbstractAn algebra A is homogeneous if the automorphism group of A acts transitively on the one dimensional subspaces of A. Suppose A is a homogeneous algebra over an infinite field k. Let La denote left multiplication by any nonzero element a ∈ A. Several results are proved concerning the structure of A in terms of La. In particular, it is shown that A decomposes as the direct sum A = ker La Im La. These results are then successfully applied to the problem of classifying the infinite homogeneous algebras of small dimension.
About a problem of Hermite and Biehler
Authors: Stoyanov Todor 
Published: April 2009

AbstractA point of departure for this paper is the famous theorem of Hermite and Biehler: If f (z) is a polynomial with complex coefficients ak and its zeros zk satisfy Im Zk < 0, then the polynomials with coefficients Re ak, and Im ak have only real zeros.We generalize this theorem for some entire functions. The entire functions in Theorem 2 and Theorem 3 are of first and second genus respectively.
Growth of functions in cercles de remplissage
Authors: Fenton P. C. , Rossi John 
Published: April 2009

AbstractSuppose that f is meromorphic in the plane, and that there is a sequence Zn → ∞ and a sequence of positive numbers ∈n → 0, such that ∈n|zn|f#(zn)/log|zn| → ∞. It is shown that if f is analytic and non-zero in the closed discs Δn = {z: |z – zn| ≦∈n|zn|}, n = 1, 2, 3 …, then, given any positive integer K, there are arbitrarily large values of n and there is a point z in Δn such that │f (z)| 〉 |Z│k. Examples are given to show that the hypotheses cannot be relaxed.
On graphC*-algebras
Authors: Goldstein P. 
Published: April 2009

AbstractCertainC*-algebras on generators and relations are associated to directed graphs. For a finite graph γ,C*-algebrais canonically isomorphic to Cuntz-Krieger algebra corresponding to the adjacency matrix of γ. It is shown that if a countably infinite graph γ is strongly connected,γis simple and purely infinite.
Free algebras in the variety of three-valued closure algebras
Authors: Abad M. , Varela J. P. Díaz 
Published: April 2009

AbstractIn this paper, the variety of three-valued closure algebras, that is, closure algebras with the property that the open elements from a three-valued Heyting algebra, is investigated. Particularly, the structure of the finitely generated free objects in this variety is determined.
Ergodic path properties of processes with stationary increments
Authors: Kella Offer , Stadje Wolfgang 
Published: April 2009

AbstractFor a real-valued ergodic process X with strictly stationary increments satisfying some measurability and continuity assumptions it is proved that the long-run ‘average behaviour’ of all its increments over finite intervals replicates the distribution of the corresponding increments of X in a strong sense. Moreover, every Lévy process has a version that possesses this ergodic path property.
On the Toeplitz algebras of right-angled and finite-type Artin groups
Authors: Crisp John , Laca Marcelo 
Published: April 2009

AbstractThe graph product of a family of groups lies somewhere between their direct and free products, with the graph determining which pairs of groups commute. We show that the graph product of quasi-lattice ordered groups is quasi-lattice ordered, and, when the underlying groups are amenable, that it satisfies Nica's amenability condition for quasi-lattice orders. The associated Toeplitz algebras have a universal property, and their representations are faithful if the generating isometries satisfy a joint properness condition. When applied to right-angled Artin groups this yields a uniqueness theorem for the C*-algebra generated by a collection of isometries such that any two of them either *-commute or else have orthogonal ranges. The analogous result fails to hold for the nonabelian Artin groups of finite type considered by Brieskorn and Saito, and Deligne.
On the absolute Nörlund summability of a Fourier series
Authors: Hsiang Fu Cheng 
Published: April 2009

Let Σn−0∞an, be a given infinite series and {sn} the sequence of its partial sums. Let {pn} be a sequence of constants, real or complex, and let us writeIfas n → ∞, then we say that the series is summable by the Nörlund method (N, pn) to σ And the series a,Σan, is said to be absolutely summable (N, pn) or summable |N, Pn| if {σn} is of bounded variation, i.e.,
On a problem of ore on maximal trees
Authors: Rao S. B. 
Published: April 2009

We consider only graphs without loops or multiple edges. Pertinent definitions are given below. For notation and other definitions we generally follow Ore [1].A connected graph G = (X, E) is said to have the property P if for every maximal tree T of G there exists a vertex aT of G such that distance between aT and x is same in T as in G for every x in X. The following problem has been posed by Ore (see [1] page 103, problem 4): Determine the graphs with property P. This paper presents a solution to the above problem in the finite case.
A note on the idempotent measures on countable semigroups
Authors: Sun Tze-Chien , Tserpes N. A. 
Published: April 2009

In [6] we announced the following
Conjecture: Let S be a locally compact semigroup and let μ be an idempotent regular probability measure on S with support F. Then(a) F is a closed completely simple subsemigroup.(b) F is isomorphic both algebraically and topologically to a paragroup ([2], p.46) X × G × Y where X and Y are locally compact left-zero and right-zero semi-groups respectively and G is a compact group. In X × G × Y the topology is the product topology and the multiplication of any two elements is defined by , x where [y, x′] is continuous mapping from Y × X → G.(c) The induced μ on X × G × Y can be decomposed as a product measure μX × μG× μY where μX and μY are two regular probability measures on X and Y respectively and μG is the normed Haar measure on G.
Additive results for the generalized Drazin inverse
Authors: Djordjević Dragan S. , Wei Yimin 
Published: April 2009

AbstractAdditive perturbation results for the generalized Drazin inverse of Banach space operators are presented. Precisely, ifAddenotes the generalized Drazin inverse of a bounded linear operatorAon an arbitrary complex Banach space, then in some special cases(A + B)dis computed in terms ofAdandBd. Thus, recent results of Hartwig, Wang and Wei (Linear Algebra Appl.322 (2001), 207–217) are extended to infinite dimensional settings with simplified proofs.
On c-normality of finite groups
Authors: Asaad M. , Mohamed M. Ezzat 
Published: April 2009

AbstractA subgroup H of a finite G is said to be c-normal in G if there exists a normal subgroup N of G such that G = HN with H ∩ N ≤ HG = CoreG(H). We are interested in studying the influence of the c–normality of certain subgroups of prime power order on the structure of finite groups.
Ado-Iwasawa extras
Authors: Barnes Donald W. 
Published: April 2009

AbstractLet L be a finite-dimensional Lie algebra over the field F. The Ado-Iwasawa Theorem asserts the existence of a finite-dimensional L-module which gives a faithful representation ρ of L. Let S be a subnormal subalgebra of L, let be a saturated formation of soluble Lie algebras and suppose that S ∈ . I show that there exists a module V with the extra property that it is -hypercentral as S-module. Further, there exists a module V which has this extra property simultaneously for every such S and , along with the Hochschild extra that ρ(x) is nilpotent for every x ∈ L with ad(x) nilpotent. In particular, if L is supersoluble, then it has a faithful representation by upper triangular matrices.
On Noetherian rings with essential socle
Authors: Chen Jianlong , Ding Nanqing , Yousif Mohamed F. 
Published: April 2009

AbstractIt is shown that if R is a right Noetherian ring whose right socle is essential as a right ideal and is contained in the left socle, then R is right Artinian. This result may be viewed as a one-sided version of a result of Ginn and Moss on two-sided Noetherian rings with essential socle. This also extends the work of Nicholson and Yousif where the same result is obtained under a stronger hypothesis. We use our work to obtain partial positive answers to some open questions on right CF, right FGF and right Johns rings.
Fitting classes and lattice formations I
Authors: Arroyo-Jordá M. , Pérez-Ramos M. D. 
Published: April 2009

AbstractA lattice formation is a class of groups whose elements are the direct product of Hall subgroups corresponding to pairwise disjoint sets of primes. In this paper Fitting classes with stronger closure properties involving F-subnormal subgroups, for a lattice formation F of full characteristic, are studied. For a subgroup-closed saturated formation G, a characterisation of the G-projectors of finite soluble groups is also obtained. It is inspired by the characterisation of the Carter subgroups as the N-projectors, N being the class of nilpotent groups.
An application of Moser iteration to complete minimal submanifolds in a sphere
Authors: Cheung Leung-Fu , Leung Pui-Fai 
Published: April 2009

AbstractWe apply the Moser iteration method to obtain a pointwise bound on the norm of the second fundamental form from a bound on its Ln norm for a complete minimal submanifold in a sphere. As an application we show that a complete minimal submanifold in a sphere with finite total curvature and Ricci curvature bounded away from -∞ must be compact. This complements similar results of Osserman and Oliveira in the case the ambient space is the Euclidean and the hyperbolic space respectively.
Boundedness of vector-valued martingale transforms on extreme points and applciations
Authors: Martínez Teresa , Torrea José L. 
Published: April 2009

AbstractLet Β1, Β2be a pair of Banach spaces andTbe a vector valued martingale transform (with respect to general filtration) which maps Β1-valued martingales into Β2-valued martingales. Then, the following statements are equivalent:Tis bounded fromintofor somep(or equivalently for everyp) in the range 1 <p< ∞;Tis bounded fromintoBMOB2;Tis bounded fromBMOB1intoBMOB2;Tis bounded frominto. Applications toUMDand martingale cotype properties are given. We also prove that the Hardy spacedefined in the case of a general filtration has nice dense sets and nice atomic decompositions if and only if Β has the Radon-Nikodým property.
Generalized Weyl's theorem and hyponormal operators
Authors: Berkani M. , Arroud A. 
Published: April 2009

AbstractLet T be a bounded linear operator acting on a Hilbert space H. The B-Weyl spectrum of T is the set σBW(T) of all λ ∈ Сsuch that T − λI is not a B-Fredholm operator of index 0. Let E(T) be the set of all isolated eigenvalues of T. The aim of this paper is to show that if T is a hyponormal operator, then T satisfies generalized Weyl's theorem σBW(T) = σ(T)/E(T), and the B-Weyl spectrum σBW(T) of T satisfies the spectral mapping theorem. We also consider commuting finite rank perturbations of operators satisfying generalized Weyl's theorem.
On the notion of residual finiteness for G-spaces
Authors: Mukherjee Goutam , Naolekar Aniruddha C. 
Published: April 2009

AbstractWe define equivariant completion of a G-complex and define residually finite G-spaces. We show that the group of G-homotopy classes of G-homotopy self equivalences of a finite, residually finite G-complex, in residually finite. This generalizes some results of Roitberg.
A note on the matrix renewal function
Authors: Kshirsagar A. M. , Gupta Y. P. 
Published: April 2009

AbstractThe Laplace-Stieltjes Transform m(s) of the matrix renewal function M(t) of a Markov Renewal process is expanded in powers of the argument s, in this paper, by using a generalized inverse of the matrix I–P0, where P0 is the transition probability matrix of the imbedded Markov chain. This helps in obtaining the values of moments of any order of the number of renewals and also of the moments of the first passage times, for large values of t, the time. All the results of renewal theory are hidden under the Laplacian curtain and this expansion helps to lift this curtain at least for large values of t and is thus useful in predicting the number of renewals.
The higher order commutators of the fractional integrals on Hardy spaces
Authors: Long Shunchao , Wang Jian 
Published: April 2009

AbstractIn this paper we investigate the boundedness on Hardy spaces for the higher order commutator Tb, m generated by the BMO function b and fractional integral type operator Tτ, and establish the boundness theorems for Tτb, m from Hp1.q1.sb, m to Lp2 and to Hp2 (0 < p1 ≤ 1), and from H Ka. p1.sq1, b, m to Ka.p2q2 and to H Ka. p2q2, respectively, for certain ranges of α, p1, q1, p2, q2 and s.
Bounds and quotient actions of innately transitive groups
Authors: Bamberg John 
Published: April 2009

AbstractFinite innately transitive permutation groups include all finite quasiprimitive and primitive permutation groups. In this paper, results in the theory of quasiprimitive and primitive groups are generalised to innately transitive groups, and in particular, we extend results of Praeger and Shalev. Thus we show that innately transitive groups possess parameter bounds which are similar to those for primitive groups. We also classify the innately transitive types of quotient actions of innately transitive groups.
Some remarks on flocks
Authors: Bader Laura , O'Keefe Christine M. , Penttila Tim 
Published: April 2009

AbstractNew proofs are given of the fundamental results of Bader, Lunardon and Thas relating flocks of the quadratic cone in PG(3, q), q odd, and BLT-sets of Q(4, q). We also show that there is a unique BLT-set of H(3, 9). The model of Penttila for Q(4, q), q odd, is extended to Q(2m, q) to construct partial flocks of size qm/2+m/2 – 1 of the cone kin PG(2m – 1, q) with vertex a point and base Q(2m – 2, q), where q is congruent to 1 or 3 modulo 8 and m is even. These partial flocks are larger than the largest previously known for m > 2. Also, the example of O'Keefe and Thas of a partial flock of k in PG(5, 3) of size 6 is generalised to a partial flock of the cone k of PG(2pn – 1, p) of size 2pn, for any prime p congruent to 1 or 3 modulo 8, with the corresponding partial BLT-set of Q(2pn, p) admitting the symmetric group of degree 2pn + 1.
Ideals of compact operators
Authors: Lima Åsvald , Oja Eve 
Published: April 2009

AbstractWe give an example of a Banach spaceXsuch thatK(X, X) is not an ideal inK(X, X**). We prove that ifz* is a weak* denting point in the unit ball of Z* and ifXis a closed subspace of a Banach spaceY, then the set of norm-preserving extensionsH B(x* ⊗z*) ⊆(Z*,Y)* of a functionalx* ⊗Z* ∈ (Z⊗X)* is equal to the setH B(x*) ⊗ {z*}. Using this result, we show that ifXis anM-ideal inYandZis a reflexive Banach space, thenK(Z, X) is anM-ideal inK(Z, Y) wheneverK(Z, X) is an ideal inK(Z, Y). We also show thatK(Z, X) is an ideal (respectively, anM-ideal) inK(Z, Y) for all Banach spaces Z whenever X is an ideal (respectively, anM-ideal) inYandX* has the compact approximation property with conjugate operators.
Involutions on finite-dimensional algebras over real closed fields
Authors: Munn W. D. 
Published: April 2009

AbstractIt is shown that the following conditions on a finite-dimensional algebra A over a real closed field or an algebraically closed field of characteristic zero are equivalent: (i) A admits a special involution, in the sense of Easdown and Munn, (ii) A admits a proper involution, (iii) A is semisimple.
Operator algebras related to Thompson's group F
Authors: Jolissaint Paul 
Published: April 2009

AbstractLet F′ be the commutator subgroup of F and let Γ0 be the cyclic group generated by the first generator of F. We continue the study of the central sequences of the factor L(F′), and we prove that the abelian von Neumann algebra L(Γ0) is a strongly singular MASA in L(F). We also prove that the natural action of F on [0, 1] is ergodic and that its ratio set is {0} ∪ {2k; k ∞ Z}.