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Notes On Null Curves In Minkowski Spaces, Makoto Sakaki Jan 2010

Notes On Null Curves In Minkowski Spaces, Makoto Sakaki

Turkish Journal of Mathematics

We show a correspondence between the evolute of a null curve and the involute of a certain spacelike curve in the 4-dimensional Minkowski space. Also we characterize pseudo-spherical null curves in the n-dimensional Minkowski space in terms of the curvature functions.


The Linear Functionals On Fundamental Locally Multiplicative Topological Algebras, E. Ansari-Piri Jan 2010

The Linear Functionals On Fundamental Locally Multiplicative Topological Algebras, E. Ansari-Piri

Turkish Journal of Mathematics

In this paper we study the dual space of fundamental locally multiplicative topological algebras and prove some results for linear and multiplicative linear functionals on these algebras. An investigation on locally compactness of the carrier space of these algebras is the last part of this note.


Cover And Contents Jan 2010

Cover And Contents

Turkish Journal of Mathematics

No abstract provided.


Cover And Contents Jan 2010

Cover And Contents

Turkish Journal of Mathematics

No abstract provided.


Stack-Sortable Permutations And Polynomials, İsmai̇l Ş. Güloğlu, Cemal Koç Jan 2009

Stack-Sortable Permutations And Polynomials, İsmai̇l Ş. Güloğlu, Cemal Koç

Turkish Journal of Mathematics

The Catalan numbers show up in a diverse variety of counting problems. In this note we give yet another characterization of the Catalan number C(n). It is characterized as the dimension of a certain space of multilinear polynomials by exhibiting a basis.


Values Of The Carmichael Function Equal To A Sum Of Two Squares, William D. Banks, Ahmet M. Güloğlu Jan 2009

Values Of The Carmichael Function Equal To A Sum Of Two Squares, William D. Banks, Ahmet M. Güloğlu

Turkish Journal of Mathematics

In this note, we determine the order of growth of the number of positive integers n \le x such that \lambda(n) is a sum of two square numbers, where \lambda(n) is the Carmichael function.


Lebesgue-Stieltjes Measure On Time Scales, Asli Deni̇z, Ünal Ufuktepe Jan 2009

Lebesgue-Stieltjes Measure On Time Scales, Asli Deni̇z, Ünal Ufuktepe

Turkish Journal of Mathematics

The theory of time scales was introduced by Stefan Hilger in his Ph. D. thesis in 1988, supervised by Bernd Auldbach, in order to unify continuous and discrete analysis [5]. Measure theory on time scales was first constructed by Guseinov [4], then further studies were made by Guseinov-Bohner [1], Cabada-Vivero [2] and Rzezuchowski [6]. In this article, we adapt the concept of Lebesgue-Stieltjes measure to time scales. We define Lebesgue-Stieltjes \Delta and \nabla-measures and by using these measures, we define an integral adapted to time scales, specifically Lebesgue-Stieltjes \Delta-integral. We also establish the relation between Lebesgue-Stieltjes measure and Lebesgue-Stieltjes \Delta-measure, …


Korovkin Type Error Estimates For Positive Linear Operators Involving Some Special Functions, Ogün Doğru, Esra Erkuş-Duman Jan 2009

Korovkin Type Error Estimates For Positive Linear Operators Involving Some Special Functions, Ogün Doğru, Esra Erkuş-Duman

Turkish Journal of Mathematics

In the present paper, we introduce a new sequence of linear positive operators with the help of generating functions. We obtain some Korovkin type approximation properties for these operators and compute rates of convergence by means of the first and second order modulus of continuities and Peetre´s K-functional. In order to obtain explicit expressions for the first and second moment of our operators, we obtain a functional differential equation including our operators. Furthermore, we deal with a modification of our operators converging to integral of function f on the interval (0,1).


Multiple Positive Solutions For Nonlinear Third-Order Boundary Value Problems In Banach Spaces, Feng Wang, Hai-Hua Lu, Fang Zhang Jan 2009

Multiple Positive Solutions For Nonlinear Third-Order Boundary Value Problems In Banach Spaces, Feng Wang, Hai-Hua Lu, Fang Zhang

Turkish Journal of Mathematics

This paper deals with the positive solutions of nonlinear boundary value problems in Banach spaces. By using fixed point index theory, some sufficient conditions for the existence of at least one or two positive solutions to boundary value problems in Banach spaces are obtained. An example illustrating the main results is given.


Cartan Calculus On The Quantum Space R_Q^3, Sali̇h Çeli̇k, E. Mehmet Özkan, Ergün Yaşar Jan 2009

Cartan Calculus On The Quantum Space R_Q^3, Sali̇h Çeli̇k, E. Mehmet Özkan, Ergün Yaşar

Turkish Journal of Mathematics

To give a Cartan calculus on the extended quantum 3d space, the noncommutative differential calculus on the extended quantum 3d space is extended by introducing inner derivations and Lie derivatives.


Strong Convergence Theorems By An Extragradient Method For Solving Variational Inequalities And Equilibrium Problems In A Hilbert Space, Poom Kumam Jan 2009

Strong Convergence Theorems By An Extragradient Method For Solving Variational Inequalities And Equilibrium Problems In A Hilbert Space, Poom Kumam

Turkish Journal of Mathematics

In this paper, we introduce an iterative process for finding the common element of the set of fixed points of a nonexpansive mapping, the set of solutions of an equilibrium problem and the set of solutions of the variational inequality for monotone, Lipschitz-continuous mappings. The iterative process is based on the so-called extragradient method. We show that the sequence converges strongly to a common element of the above three sets under some parametric controlling conditions. This main theorem extends a recent result of Yao, Liou and Yao [Y. Yao, Y. C. Liou and J.-C. Yao, ''An Extragradient Method for Fixed …


Cover And Contents Jan 2009

Cover And Contents

Turkish Journal of Mathematics

No abstract provided.


On Symmetric Monomial Curves In P^3, Mesut Şahi̇n Jan 2009

On Symmetric Monomial Curves In P^3, Mesut Şahi̇n

Turkish Journal of Mathematics

In this paper, we give an elementary proof of the fact that symmetric arithmetically Cohen-Macaulay monomial curves are set-theoretic complete intersections. The proof is constructive and provides the equations of the surfaces cutting out the monomial curve.


On \Tau-Lifting Modules And \Tau-Semiperfect Modules, Mustafa Alkan Jan 2009

On \Tau-Lifting Modules And \Tau-Semiperfect Modules, Mustafa Alkan

Turkish Journal of Mathematics

Motivated by [1], we study on \tau-lifting modules (rings) and \tau-semiperfect modules (rings) for a preradical \tau and give some equivalent conditions. We prove that; i) if M is a projective \tau-lifting module with \tau(M) \subseteq \delta(M), then M has the finite exchange property; ii) if R is a left hereditary ring and \tau is a left exact preradical, then every \tau-semiperfect module is \tau--lifting; iii) R is \tau-lifting if and only if every finitely generated free module is \tau-lifting if and only if every finitely generated projective module is \tau-lifting; iv) if \tau (R) \subseteq \delta (R), then R …


The Existence Of Triple Positive Solutions Of Nonlinear Four-Point Boundary Value Problem With P-Laplacian, Xiang-Feng Li, Pei-Hao Zhao Jan 2009

The Existence Of Triple Positive Solutions Of Nonlinear Four-Point Boundary Value Problem With P-Laplacian, Xiang-Feng Li, Pei-Hao Zhao

Turkish Journal of Mathematics

This paper deals with the multiplicity results of positive solutions of one-dimensional singular p-Laplace equation (\varphi_p(u'(t)))'+a(t)f(t,u(t),u'(t))=0, 0


Perturbation Of Closed Range Operators, Mohammad Sal Moslehian, Ghadir Sadeghi Jan 2009

Perturbation Of Closed Range Operators, Mohammad Sal Moslehian, Ghadir Sadeghi

Turkish Journal of Mathematics

Let T, A be operators with domains D(T) \subseteq D(A) in a normed space X. The operator A is called T-bounded if Ax \leq a x +b Tx for some a, b\geq 0 and all x \in D(T). If A has the Hyers--Ulam stability then under some suitable assumptions we show that both T and S: = A+T have the Hyers--Ulam stability. We also discuss the best constant of Hyers--Ulam stability for the operator S. Thus we establish a link between T-bounded operators and Hyers--Ulam stability.


Modified Szász-Mirakjan-Kantorovich Operators Preserving Linear Functions, Oktay Duman, Mehmet Ali̇ Özarslan, Biancamaria Della Vecchia Jan 2009

Modified Szász-Mirakjan-Kantorovich Operators Preserving Linear Functions, Oktay Duman, Mehmet Ali̇ Özarslan, Biancamaria Della Vecchia

Turkish Journal of Mathematics

In this paper, we introduce a modification of the Szász-Mirakjan-Kantorovich operators, which preserve the linear functions. This type of operator modification enables better error estimation on the interval [1/2,+\infty) than the classical Szász-Mirakjan-Kantorovich operators. We also obtain a Voronovskaya-type theorem for these operators.


Equi-Statistical Extension Of The Korovkin Type Approximation Theorem, Sevda Karakuş, Kami̇l Demi̇rci̇ Jan 2009

Equi-Statistical Extension Of The Korovkin Type Approximation Theorem, Sevda Karakuş, Kami̇l Demi̇rci̇

Turkish Journal of Mathematics

In this paper using equi-statistical convergence, which is stronger than the usual uniform convergence and statistical uniform convergence, we obtain a general Korovkin type theorem. Then, we construct examples such that our new approximation result works but its classical and statistical cases do not work.


A New Approach On Constant Angle Surfaces In E^3, Marian Ioan Munteanu, Ana Irina Nistor Jan 2009

A New Approach On Constant Angle Surfaces In E^3, Marian Ioan Munteanu, Ana Irina Nistor

Turkish Journal of Mathematics

In this paper we study constant angle surfaces in Euclidean 3--space. Even that the result is a consequence of some classical results involving the Gauss map (of the surface), we give another approach to classify all surfaces for which the unit normal makes a constant angle with a fixed direction.


Applications Of The Golden Ratio On Riemannian Manifolds, Cristina-Elena Hretcanu, Mircea Craşmareanu Jan 2009

Applications Of The Golden Ratio On Riemannian Manifolds, Cristina-Elena Hretcanu, Mircea Craşmareanu

Turkish Journal of Mathematics

The Golden Ratio is a fascinating topic that continually generates new ideas. The main purpose of the present paper is to point out and find some applications of the Golden Ratio and of Fibonacci numbers in Differential Geometry. We study a structure defined on a class of Riemannian manifolds, called by us a Golden Structure. A Riemannian manifold endowed with a Golden Structure will be called a Golden Riemannian manifold. Precisely, we say that an (1,1)-tensor field \widetilde{P} on a m-dimensional Riemannian manifold (\widetilde{M}, \widetilde{g}) is a Golden Structure if it satisfies the equation \widetilde{P}^{2}=\widetilde{P}+I (which is similar to that …


Cover And Contents Jan 2009

Cover And Contents

Turkish Journal of Mathematics

No abstract provided.


Criteria Of Nilpotency And Influence Of Contranormal Subgroups On The Structure Of Infinite Groups, Leonid Andreevich Kurdachenko, Javier Otal, Igor Yakov Subbotin Jan 2009

Criteria Of Nilpotency And Influence Of Contranormal Subgroups On The Structure Of Infinite Groups, Leonid Andreevich Kurdachenko, Javier Otal, Igor Yakov Subbotin

Turkish Journal of Mathematics

Following J.S. Rose, a subgroup H of a group G is called contranormal if G=H^G. In a certain sense, contranormal subgroups are antipodes to subnormal subgroups. It is well known that a finite group is nilpotent if and only if it has no proper contranormal subgroups. However, for infinite groups this criterion is not valid. There are examples of non-nilpotent infinite groups whose subgroups are subnormal; in particular, these groups have no contranormal subgroups. Nevertheless, for some classes of infinite groups, the absence of contranormal subgroups implies nilpotency of the group. The present article is devoted to the search of …


Some Inequalities Concerning The Rate Of Growth Of Polynomials, Abdullah Mir, K. K. Dewan, Naresh Singh Jan 2009

Some Inequalities Concerning The Rate Of Growth Of Polynomials, Abdullah Mir, K. K. Dewan, Naresh Singh

Turkish Journal of Mathematics

In this paper we consider a class of polynomials p(z)=a_0+\suml_{v=t}^n a_vz^v, t\ge1, not vanishing in z


Strong Differential Subordination, Georgia Irina Oros, Gheorghe Oros Jan 2009

Strong Differential Subordination, Georgia Irina Oros, Gheorghe Oros

Turkish Journal of Mathematics

The concept of differential subordination was introduced in [4] by S. S. Miller and P. T. Mocanu and the concept of strong differential subordination was introduced in [1] by J. A. Antonino and S. Romaguera. This last concept was applied in the special case of Briot-Bouquet strong differential subordination. In this paper we study the strong differential subordinations in the general case, following the general theory of differential subordinations presented in [4].


On The Geometry Of Null Curves In The Minkowski 4-Space, Recep Aslaner, A. İhsan Boran Jan 2009

On The Geometry Of Null Curves In The Minkowski 4-Space, Recep Aslaner, A. İhsan Boran

Turkish Journal of Mathematics

In this paper, we study the basic results on the general study of null curves in the Minkowski 4-space R_1^4. A transversal vector bundle of a null curve in R_1^4 is constructed using a frenet Frame consisting of two real null and two space-like vectors. The null curves are characterized by using the Frenet frame.


Approximation By Certain Linear Operators Preserving X^2, Lucyna Rempulska, Karolina Tomczak Jan 2009

Approximation By Certain Linear Operators Preserving X^2, Lucyna Rempulska, Karolina Tomczak

Turkish Journal of Mathematics

We investigate certain positive linear operators L_n preserving the functions e_k (x)=x^k, k=0, 1, and modified operators L_n^* which preserve e_0 and e_2. We show that the error of approximation of f by L_n^* (f) is smaller than for L_n(f).


Partial Open Book Decompositions And The Contact Class In Sutured Floer Homology, Tolga Etgü, Burak Özbağci Jan 2009

Partial Open Book Decompositions And The Contact Class In Sutured Floer Homology, Tolga Etgü, Burak Özbağci

Turkish Journal of Mathematics

We demonstrate how to combinatorially calculate the EH-class of a compatible contact structure in the sutured Floer homology group of a balanced sutured three manifold which is associated to an abstract partial open book decomposition. As an application we show that every contact three manifold (closed or with convex boundary) can be obtained by gluing tight contact handlebodies whose EH-classes are nontrivial.


Cover And Contents Jan 2009

Cover And Contents

Turkish Journal of Mathematics

No abstract provided.


Uniqueness For Meromorphic Functions And Differential Polynomials, Chao Meng Jan 2009

Uniqueness For Meromorphic Functions And Differential Polynomials, Chao Meng

Turkish Journal of Mathematics

In this article, we deal with the uniqueness problems on meromorphic functions concerning differential polynomials and prove the following result: Let f and g be two transcendental meromorphic functions, \alpha be a meromorphic function such that T(r,\alpha)=o(T(r,f)+T(r,g)) and \alpha \not\equiv 0,\infty. Let a be a nonzero constant. Suppose that m,n are positive integers such that n>m+10. If \Psi_f' and \Psi_g' share ``(0,2)", then (i) if m\geq 2, then f(z)\equiv g(z); (ii) if m=1, either f(z)\equiv g(z) or f and g satisfy the algebraic equation R(f,g)\equiv 0, where R(\varpi_1,\varpi_2)=(n+1)(\varpi_1^{n+2}-\varpi_2^{n+2})-(n+2)(\varpi_1^{n+1} -\varpi_2^{n+1}). The results in this paper improve the results of Xiong-Lin-Mori …


C1 Modules With Respect To A Hereditary Torsion Theory, Tahi̇re Özen Jan 2009

C1 Modules With Respect To A Hereditary Torsion Theory, Tahi̇re Özen

Turkish Journal of Mathematics

An R-module M is said to be a C1-module if every closed submodule of M is a direct summand. In this paper we introduce and investigate the concept of the \tau-C1 module for a hereditary torsion theory \tau on Mod-R. \tau-C1 modules are a generalization of C1-modules.