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Full-Text Articles in Mathematics

Radical Anti-Invariant Lightlike Submanifolds Of Semi-Riemannian Product Manifolds, Erol Kiliç, Bayram Şahi̇n Jan 2008

Radical Anti-Invariant Lightlike Submanifolds Of Semi-Riemannian Product Manifolds, Erol Kiliç, Bayram Şahi̇n

Turkish Journal of Mathematics

We introduce radical anti-invariant lightlike submanifolds of a semi Riemannian product manifold and give examples. After we obtain the conditions of integrability of distributions which are involved in the definition of radical anti-invariant lightlike submanifolds, we investigate the geometry of leaves of distributions. We also obtain the induced connection is a metric connection and a radical anti-invariant lightlike submanifold is a product manifold under certain conditions. Finally, we study totally umbilical radical anti-invariant lightlike submanifolds and observe that they are totally geodesic under a condition.


Best P-Simultaneous Approximation In Some Metric Space, Mona Khandaqji, Wasfi Shatanawi Jan 2008

Best P-Simultaneous Approximation In Some Metric Space, Mona Khandaqji, Wasfi Shatanawi

Turkish Journal of Mathematics

Let X be a Banach space, (I,\mu) be a finite measure space, and \Phi be an increasing subadditive continuous function on [0,+\infty) with \Phi(0)=0. In the present paper, we discuss the best p-simultaneous approximation of L^\Phi(I,G) in L^\Phi(I,X) where G is a closed subspace of X.


Lyapunov-Type Inequalities For Certain Nonlinear Systems On Time Scales, Mehmet Ünal, Devri̇m Çakmak Jan 2008

Lyapunov-Type Inequalities For Certain Nonlinear Systems On Time Scales, Mehmet Ünal, Devri̇m Çakmak

Turkish Journal of Mathematics

In this study, we prove Lyapunov-type inequalities for certain nonlinear systems on an arbitrary time scale T by using elementary time scale calculus. These inequalities enable us to obtain a criterion of disconjugacy for such systems. Special cases of our results contain the classical Lyapunov inequality for both differential and difference equations.


Essential Spectra Of Composition Operators On The Space Of Bounded Analytic Functions, Uğur Gül Jan 2008

Essential Spectra Of Composition Operators On The Space Of Bounded Analytic Functions, Uğur Gül

Turkish Journal of Mathematics

In this small note we characterize the essential spectra of a class of composition operators on H^{\infty}(H) of the upper half-plane H and on H^{\infty}(D) of the unit disc D. These composition operators are induced by perturbations of translations


Some Characterizations Of Rectifying Curves In The Euclidean Space E^4, Kazim İlarslan, Emilija Nesovic Jan 2008

Some Characterizations Of Rectifying Curves In The Euclidean Space E^4, Kazim İlarslan, Emilija Nesovic

Turkish Journal of Mathematics

In this paper, we define a rectifying curve in the Euclidean 4-space as a curve whose position vector always lies in orthogonal complement N^{\perp} of its principal normal vector field N. In particular, we study the rectifying curves in E^4 and characterize such curves in terms of their curvature functions.


Linear Connections On Light-Like Manifolds, Teki̇n Dereli̇, Şahi̇n Koçak, Murat Li̇moncu Jan 2008

Linear Connections On Light-Like Manifolds, Teki̇n Dereli̇, Şahi̇n Koçak, Murat Li̇moncu

Turkish Journal of Mathematics

It is well-known that a torsion-free linear connection on a light-like manifold (M,g) compatible with the degenerate metric g exists if and only if Rad(TM) is a Killing distribution. In case of existence, there is an infinitude of connections with none distinguished. We propose a method to single out connections with the help of a special set of 1-forms by the condition that the 1-forms become parallel with respect to this connection. Such sets of 1-forms could be regarded as an additional structure imposed upon the light-like manifold. We consider also connections with torsion and with non-metricity on light-like manifolds.


Basic Properties And Multipliers Space On L^{1}(G)\Cap L(P,Q)(G) Spaces, İlker Eryilmaz, Cenap Duyar Jan 2008

Basic Properties And Multipliers Space On L^{1}(G)\Cap L(P,Q)(G) Spaces, İlker Eryilmaz, Cenap Duyar

Turkish Journal of Mathematics

Let G be locally compact Abelian group with Haar measure. First is discussed some properties of L^{1}(G) \cap L(p,q)(G) spaces. Then is mentioned the multipliers space on L^{1}(G) \cap L(p,q) (G) spaces.


On Some Algebraic Properties Of Semi-Discrete Hyperbolic Type Equations, İsmagi̇l Habibullin, Asli Pekcan, Natalya Zheltukhina Jan 2008

On Some Algebraic Properties Of Semi-Discrete Hyperbolic Type Equations, İsmagi̇l Habibullin, Asli Pekcan, Natalya Zheltukhina

Turkish Journal of Mathematics

Nonlinear semi-discrete equations of the form t_x(n+1) = f(t(n), t(n+1), t_x(n)) are studied. An adequate algebraic formulation of the Darboux integrability is discussed and an attempt to adopt this notion to the classification of Darboux integrable chains has been undertaken.


Posner´S Second Theorem And An Annihilator Condition With Generalized Derivations, Vincenzo De Filippis Jan 2008

Posner´S Second Theorem And An Annihilator Condition With Generalized Derivations, Vincenzo De Filippis

Turkish Journal of Mathematics

Let R be a prime ring of characteristic different from 2, with extended centroid C, U its two-sided Utumi quotient ring, \delta\neq 0 a non-zero generalized derivation of R, f(x_1,..,x_n) a non-central multilinear polynomial over C in n non-commuting variables, a \in R such that a[\delta(f(r_1,..,r_n)),f(r_1,..,r_n)]=0, for any r_1,..,r_n \in R. Then one of the following holds: 1. a=0; 2. there exists \lambda \in C such that \delta(x)=\lambda x, for all x \in R; 3. there exist q \in U and \lambda \in C such that \delta(x)=(q+\lambda)x+xq, for all x\in R, and f(x_1,..,x_n)^2 is central valued on R.


Diametral Dimension And Köthe Spaces, Tosun Terzi̇oğlu Jan 2008

Diametral Dimension And Köthe Spaces, Tosun Terzi̇oğlu

Turkish Journal of Mathematics

We generalize some well-known results about the diametral dimension of classical Köthe spaces


On The Distribution Of Random Dirichlet Series In The Whole Plane, Qiyu Jin, Daochun Sun Jan 2008

On The Distribution Of Random Dirichlet Series In The Whole Plane, Qiyu Jin, Daochun Sun

Turkish Journal of Mathematics

For some random Dirichlet series of order(R) infinite almost surely, every horizontal line is a strong Borel line of order(R) infinite and without exceptional Little functions.


Sufficient Conditions For The Lp-Equivalence Between Two Nonlinear Impulse Differential Equations, A. Georgieva, S. Kostadinov Jan 2008

Sufficient Conditions For The Lp-Equivalence Between Two Nonlinear Impulse Differential Equations, A. Georgieva, S. Kostadinov

Turkish Journal of Mathematics

Sufficient conditions for the Lp-equivalence between two nonlinear impulse differential equations with unbounded linear parts and possibly unbounded nonlinearity parts are given. An example of two nonlinear impulse differential parabolic equations is considered.


Trace Classes And Fixed Points For The Extended Modular Group \Overline{\Gamma}, Özden Koruoğlu, Recep Şahi̇n, Sebahatti̇n İki̇kardeş Jan 2008

Trace Classes And Fixed Points For The Extended Modular Group \Overline{\Gamma}, Özden Koruoğlu, Recep Şahi̇n, Sebahatti̇n İki̇kardeş

Turkish Journal of Mathematics

The extended modular group \overline{\Gamma}=PGL(2,\mathbb{Z}) is the group obtained by adding the reflection R(z)=1/\overline{z} to the generators of the modular group \Gamma =PSL(2, {Z}). In this paper, we find the trace classes of the extended modular group \overline{\Gamma}. Using this, we classify the elements of \overline{\Gamma}.


On The Regular Elements In Z_N, Osama Alkam, Emad Abu Osba Jan 2008

On The Regular Elements In Z_N, Osama Alkam, Emad Abu Osba

Turkish Journal of Mathematics

All rings are assumed to be finite commutative with identity element. An element a \in R is called a regular element if there exists b \in R such that a=a^2b, the element b is called a von Neumann inverse for a. A characterization is given for regular elements and their inverses in Z_n, the ring of integers modulo n. The arithmetic function V(n), which counts the regular elements in Z_n is studied. The relations between V(n) and Euler's phi-function \varphi (n) are explored.


A Decomposition Method For Solving Unsteady Convection-Diffusion Problems, Shaher Momani Jan 2008

A Decomposition Method For Solving Unsteady Convection-Diffusion Problems, Shaher Momani

Turkish Journal of Mathematics

In this study, a decomposition method for approximating the solutions of unsteady convection-diffusion problems is implemented. The approximate solution is calculated in the form of a convergent series with easily computable components. The calculations are accelerated by using the noise terms phenomenon for nonhomogeneous problems. Numerical examples are investigated to illustrate the pertinent features of the proposed algorithm.


Mirror Principle For Flag Manifolds, Vehbi̇ Emrah Paksoy Jan 2008

Mirror Principle For Flag Manifolds, Vehbi̇ Emrah Paksoy

Turkish Journal of Mathematics

In this paper, using mirror principle developped by Lian, Liu and Yau [8, 9, 10, 11, 12, 13] we obtained the A and B series for the equivariant tangent bundles over homogenous spaces using Chern polynomial. This is necessary to obtain related cohomology valued series for given arbitrary vector bundle and multiplicative characteristic class. Moreover, this can be used as a valuable testing ground for the theories which associates quantum cohomologies and J functions of non-abelian quotient to abelian quotients via quantization.


Mixed Type Of Integral Equation With Potential Kernel, Mohamed Abdella A. Abdou, Gamal Mohamed Abd Al-Kader Jan 2008

Mixed Type Of Integral Equation With Potential Kernel, Mohamed Abdella A. Abdou, Gamal Mohamed Abd Al-Kader

Turkish Journal of Mathematics

This paper presents the solution of an integral equation of a mixed type in three-dimensions in the space L_2 (\Omega) \times C[0,T], where T < \infty, and \Omega is the domain of integration with respect to position. The kernel of position integral term is considered in the potential function form, while the kernel of time is considered as a continuous kernel. A linear system of Fredholm integral equations of the first and second kinds are obtained and solved. Krein's method is used to solve the Fredholm integral equation of the first kind, while the second kind is solved numerically.


A Note On A Problem Of J. Galambos, Lu-Ming Shen, Yue-Hua Liu, Yu-Yuan Zhou Jan 2008

A Note On A Problem Of J. Galambos, Lu-Ming Shen, Yue-Hua Liu, Yu-Yuan Zhou

Turkish Journal of Mathematics

For any x\in (0,1], letx = \frac{1}{d_1} + \frac{a_1}{b_1} \frac{1}{d_2} + ··· + \frac{a_1a_2 ··· a_n}{b_1b_2 ··· b_n} \frac{1}{d_{n+1}} + ··· be the Oppenheim series expansion of x. In this paper, we investigate the Hausdorff dimension of the set B_m={x:1


Cover For Modules And Injective Modules, N. Amiri Jan 2008

Cover For Modules And Injective Modules, N. Amiri

Turkish Journal of Mathematics

Let R be a commutative ring with identity and M be an R-module with Spec(M) \neq \phi. A cover of the R-submodule K of M is a subset C of Spec(M) satisfying that for any x \in K, x \neq 0, there is N \in C such that ann(x) \subset (N:M). If we denote by J = \bigcap_{N \in C} (N:M) and assume that M is finitely generated, then JM=M implies that M=0, M is called C-injective provided each R-homomorphism \phi : (N:M) \rightarrow M with N \in C can be lifted to an R-homomorphism \lambda : R \rightarrow M. …


Nonexistence Of Stable Exponentially Harmonic Maps From Or Into Compact Convex Hypersurfaces In R^{M+1}, Jiancheng Liu Jan 2008

Nonexistence Of Stable Exponentially Harmonic Maps From Or Into Compact Convex Hypersurfaces In R^{M+1}, Jiancheng Liu

Turkish Journal of Mathematics

In this paper, we study the nonexistence problems for stable exponentially harmonic map into or from compact convex hypersurface M^m \subset R^{m+1}, and show that every nonconstant exponentially harmonic map f, between M^m and any compact Riemannian manifold, is unstable if (4) holds.


On Non-Existence Of Lightlike Hypersurfaces Of Indefinite Kenmotsu Space Form, Nesi̇p Aktan Jan 2008

On Non-Existence Of Lightlike Hypersurfaces Of Indefinite Kenmotsu Space Form, Nesi̇p Aktan

Turkish Journal of Mathematics

In this paper, lightlike hypersurfaces of indefinite Kenmotsu space form are studied. Some characterizations of non-existence of lightlike hypersurfaces of indefinite Kenmotsu space form are given.


Cr-Submanifolds Of An S-Manifold, A. Alghanemi Jan 2008

Cr-Submanifolds Of An S-Manifold, A. Alghanemi

Turkish Journal of Mathematics

The study of CR-submanifolds of a Kaehler manifold was initiated by Bejancu [1]. Since then many papers have appeared on CR-submanifolds. The purpose of this paper is to studied the CR-submanifolds of an S-manifold. In particular, we studied the integrability of the distributions D and D^{\bot} of a CR-submanifold of an S-manifold.


Real Gromov-Witten Invariants On The Moduli Space Of Genus 0 Stable Maps To A Smooth Rational Projective Space, Seongchun Kwon Jan 2008

Real Gromov-Witten Invariants On The Moduli Space Of Genus 0 Stable Maps To A Smooth Rational Projective Space, Seongchun Kwon

Turkish Journal of Mathematics

We characterize transversality, non-transversality properties on the moduli space of genus 0 stable maps to a rational projective surface. If a target space is equipped with a real structure, i.e, anti-holomorphic involution, then the results have real enumerative applications. Firstly, we can define a real version of Gromov-Witten invariants. Secondly, we can prove the invariance of Welschinger's invariant in algebraic geometric category.


Proximinality In L^1(I,X), Sharifa Al-Sharif, R. Khalil Jan 2008

Proximinality In L^1(I,X), Sharifa Al-Sharif, R. Khalil

Turkish Journal of Mathematics

Let X be a Banach space and let (I,\Omega ,\mu) be a measure space. For 1 \leq p < \infty, let L^p(I,X) denote the space of Bochner p-integrable functions defined on I with values in X. The object of this paper is to give sufficient conditions for the proximinality of L^1(I,H)+L^1(I,G) in L^1(I,X), where H and G are two proximinal subspaces of X which include as a special case the proximality of L^1(I) \stackrel{\wedge}{\otimes} G + H \stackrel{\wedge}{\otimes} L^1(I) in L^1(I \times I).


Metric Trees, Hyperconvex Hulls And Extensions, Asuman G. Aksoy, B. Maurizi Jan 2008

Metric Trees, Hyperconvex Hulls And Extensions, Asuman G. Aksoy, B. Maurizi

Turkish Journal of Mathematics

In this paper we examine the relationship between hyperconvex hulls and metric trees. After providing a linking construction for hyperconvex spaces, we show that the four-point property is inherited by the hyperconvex hull, which leads to the theorem that every complete metric tree is hyperconvex. We also consider some extension theorems for these spaces.


On Certain Type Of Modular Sequence Spaces, Manjul Gupta, Shesadev Pradhan Jan 2008

On Certain Type Of Modular Sequence Spaces, Manjul Gupta, Shesadev Pradhan

Turkish Journal of Mathematics

In this paper we consider a particular type of modular sequence spaces defined with the help of a given sequence \alpha = {\alpha_n} of strictly positive real numbers \alpha_n's and an Orlicz function M. Indeed, if we define M_n(x) = M(\alpha_nx) and \tildeM_n(x)=M(x/\alpha_n), x\in[0, \infty), we consider the modular sequence spaces l{M_n} and l{\tildeM_n}, denoted by l_M^{\alpha} and l_{\alpha}^M respectively. These are known to be BK-spaces and if M satisfies \Delta_2-condition, they are AK-spaces as well. However, if we consider the spaces l_{\alpha}^M and l_n^{\alpha} corresponding to two complementary Orlicz functions M and N satisfying \Delta_2-condition, they are perfect sequence …


On Generalized Solution Of A Class Of Higher Order Operator-Differential Equations, Rovshan Z. Gumbataliev Jan 2008

On Generalized Solution Of A Class Of Higher Order Operator-Differential Equations, Rovshan Z. Gumbataliev

Turkish Journal of Mathematics

In this paper the sufficient conditions on the existence and uniqueness of a generalized solution on the axis are obtained for higher order operator-differential equations, the main part of which is multi characteristic.


Primary Finitely Compactly Packed Modules And S-Avoidance Theorem For Modules, Arwa Eid Ashour Jan 2008

Primary Finitely Compactly Packed Modules And S-Avoidance Theorem For Modules, Arwa Eid Ashour

Turkish Journal of Mathematics

In this paper we introduce the concept of primary finitely compactly packed modules, which generalizes the concept of primary compactly packed modules. We first find the conditions that make the primary finitely compactly packed modules primary compactly packed. Also, several results on the primary finitely compactly packed modules are proved. In addition, the necessary and sufficient conditions for an R-module M to be primary finitely compactly packed are investigated. Finally, we introduce the S-Avoidance Theorem for modules.


Killing And Geodesic Lightlike Hypersurfaces Of Indefinite Sasakian Manifolds, Fortune Massamba Jan 2008

Killing And Geodesic Lightlike Hypersurfaces Of Indefinite Sasakian Manifolds, Fortune Massamba

Turkish Journal of Mathematics

In this paper, we study a lightlike hypersurface of indefinite Sasakian manifold, tangent to the structure vector field \xi. Theorems on parallel and Killing distributions are obtained. Necessary and sufficient conditions have been given for lightlike hypersurface to be mixed totally geodesic, D-totally geodesic, D\perp-totally geodesic and D'-totally geodesic. We prove that, if the screen distribution of lightlike hypersurface M of indefinite Sasakian manifold is totally umbilical, the D\perp-geodesibility of M is equivalent to the D\perp-parallelism of the distribution T M^\perp of rank 1 (Theorem \ref{Theoscre}). Finally, we give the D\perp-version (Theorem 4.22) of the Theorem 2.2 ([11], page 88).


A Condition For Warped Product Semi-Invariant Submanifolds To Be Riemannian Product Semi-Invariant Submanifolds In Locally Riemannian Product Manifolds, Mehmet Atçeken Jan 2008

A Condition For Warped Product Semi-Invariant Submanifolds To Be Riemannian Product Semi-Invariant Submanifolds In Locally Riemannian Product Manifolds, Mehmet Atçeken

Turkish Journal of Mathematics

In this article, we give a necessary and sufficient condition for warped product semi-invariant submanifolds to be Riemannian product semi-invariant submanifolds in a locally Riemannian product manifold whose factor manifolds are real space form.