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Full-Text Articles in Physical Sciences and Mathematics

Essential Norms Of Weighted Composition Operators Between Zygmund-Type Spaces And Bloch-Type Spaces, Amir Hossein Sanatpour, Mostafa Hassanlou Jan 2014

Essential Norms Of Weighted Composition Operators Between Zygmund-Type Spaces And Bloch-Type Spaces, Amir Hossein Sanatpour, Mostafa Hassanlou

Turkish Journal of Mathematics

We investigate the boundedness of weighted composition operator u C_{\varphi} mapping the Zygmund-type space Z^{\alpha} into the Bloch-type space B^{\beta}. Then we give essential norm estimates of such an operator in terms of u and \varphi.


General Rotational Surfaces In The 4-Dimensional Minkowski Space, Georgi Ganchev, Velichka Milousheva Jan 2014

General Rotational Surfaces In The 4-Dimensional Minkowski Space, Georgi Ganchev, Velichka Milousheva

Turkish Journal of Mathematics

General rotational surfaces as a source of examples of surfaces in the 4-dimensional Euclidean space were introduced by C. Moore. In this paper we consider the analogue of these surfaces in the Minkowski 4-space. On the basis of our invariant theory of spacelike surfaces we study general rotational surfaces with special invariants. We describe analytically the flat general rotational surfaces and the general rotational surfaces with flat normal connection. We classify completely the minimal general rotational surfaces and the general rotational surfaces consisting of parabolic points.


A Characterization Of The Projective Transformation In Minkowski 3-Space, Yasemi̇n Alagöz Jan 2014

A Characterization Of The Projective Transformation In Minkowski 3-Space, Yasemi̇n Alagöz

Turkish Journal of Mathematics

We consider transformations preserving asymptotic directions of surfaces in Minkowski 3-space and show that a transformation preserves the asymptotic directions of a surface if only if it is the projective one. Therefore, we obtain a characterization of the projective transformation.


The Property Of Real Hypersurfaces In 2-Dimensional Complex Space Form With Ricci Operator, Dong Ho Lim, Woon Ha Sohn, Seong Soo Ahn Jan 2014

The Property Of Real Hypersurfaces In 2-Dimensional Complex Space Form With Ricci Operator, Dong Ho Lim, Woon Ha Sohn, Seong Soo Ahn

Turkish Journal of Mathematics

Let M be a real hypersurface in a complex space form M_2(c), c \neq 0. In this paper, we prove that S \phi=\phi S on M if and only if M is pseudo-Einstein.


Population Dynamical Behaviors Of Stochastic Logistic System With Jumps, Ruihua Wu, Ke Wang Jan 2014

Population Dynamical Behaviors Of Stochastic Logistic System With Jumps, Ruihua Wu, Ke Wang

Turkish Journal of Mathematics

This paper is concerned with a stochastic logistic model driven by martingales with jumps. In the model, generalized noise and jump noise are taken into account. This model is new and more feasible. The explicit global positive solution of the system is presented, and then sufficient conditions for extinction and persistence are established. The critical value of extinction, nonpersistence in the mean, and weak persistence in the mean are obtained. The path-wise and moment properties are also investigated. Finally, some simulation figures are introduced to illustrate the main results.


On A Generalization Of Kelly's Combinatorial Lemma, Aymen Ben Amira, Jamel Dammak, Hamza Si Kaddour Jan 2014

On A Generalization Of Kelly's Combinatorial Lemma, Aymen Ben Amira, Jamel Dammak, Hamza Si Kaddour

Turkish Journal of Mathematics

Kelly's combinatorial lemma is a basic tool in the study of Ulam's reconstruction conjecture. A generalization in terms of a family of t -elements subsets of a v -element set was given by Pouzet. We consider a version of this generalization modulo a prime p. We give illustrations to graphs and tournaments.


Frobenius-Like Groups As Groups Of Automorphisms, Güli̇n Ercan, İsmai̇l Şuayi̇p Güloğlu, Evgeny Khukhro Jan 2014

Frobenius-Like Groups As Groups Of Automorphisms, Güli̇n Ercan, İsmai̇l Şuayi̇p Güloğlu, Evgeny Khukhro

Turkish Journal of Mathematics

A finite group FH is said to be Frobenius-like if it has a nontrivial nilpotent normal subgroup F with a nontrivial complement H such that FH/[F,F] is a Frobenius group with Frobenius kernel F/[F,F]. Such subgroups and sections are abundant in any nonnilpotent finite group. We discuss several recent results about the properties of a finite group G admitting a Frobenius-like group of automorphisms FH aiming at restrictions on G in terms of C_G(H) and focusing mainly on bounds for the Fitting height and related parameters. Earlier such results were obtained for Frobenius groups of automorphisms; new theorems for Frobenius-like …


Hilbert Series Of The Braid Monoid Mb_4 In Band Generators, Zaffar Iqbal, Shamaila Yousaf Jan 2014

Hilbert Series Of The Braid Monoid Mb_4 In Band Generators, Zaffar Iqbal, Shamaila Yousaf

Turkish Journal of Mathematics

L. A. Bokut gave a Gröbner--Shirshov basis of the braid group B_n in band generators. Using this presentation and solving all the ambiguities we construct a linear system for irreducible words and compute the Hilbert series of the braid monoid MB_4.


A Cohen Type Inequality For Laguerre--Sobolev Expansions With A Mass Point Outside Their Oscillatory Regime, Edmundo José Huertas Cejudo, Francisco Marcellán Espanol, María Francisca Pérez Valero, Yamilet Quintana Jan 2014

A Cohen Type Inequality For Laguerre--Sobolev Expansions With A Mass Point Outside Their Oscillatory Regime, Edmundo José Huertas Cejudo, Francisco Marcellán Espanol, María Francisca Pérez Valero, Yamilet Quintana

Turkish Journal of Mathematics

Let consider the Sobolev type inner product \langle f, g\rangle_S = \int_0^{\infty} f(x)g(x)d \mu (x) + Mf(c)g(c) + Nf^{\prime}(c) g^{\prime}(c), where d\mu (x) = x^{\alpha} e^{-x}dx, \alpha > -1, is the Laguerre measure, c < 0, and M, N \geq 0. In this paper we get a Cohen-type inequality for Fourier expansions in terms of the orthonormal polynomials associated with the above Sobolev inner product. Then, as an immediate consequence, we deduce the divergence of Fourier expansions and Cesàro means of order \delta in terms of this kind of Laguerre--Sobolev polynomials.


Pseudosymmetric Lightlike Hypersurfaces, Sema Kazan, Bayram Şahi̇n Jan 2014

Pseudosymmetric Lightlike Hypersurfaces, Sema Kazan, Bayram Şahi̇n

Turkish Journal of Mathematics

We study lightlike hypersurfaces of a semi-Riemannian manifold satisfying pseudosymmetry conditions. We give sufficient conditions for a lightlike hypersurface to be pseudosymmetric and show that there is a close relationship of the pseudosymmetry condition of a lightlike hypersurface and its integrable screen distribution. We obtain that a pseudosymmetric lightlike hypersurface is a semisymmetric lightlike hypersurface or totally geodesic under certain conditions. Moreover, we give an example of pseudosymmetric lightlike hypersurfaces and investigate pseudoparallel lightlike hypersurfaces. Furthermore, we introduce Ricci-pseudosymmetric lightlike hypersurfaces, obtain characterizations, and give an example for such hypersurfaces.


On The Equivariant Cohomology Algebra For Solenoidal Actions, Ali̇ Arslan Özkurt Jan 2014

On The Equivariant Cohomology Algebra For Solenoidal Actions, Ali̇ Arslan Özkurt

Turkish Journal of Mathematics

We prove, under certain conditions, that if a solenoidal group (i.e. 1-dimensional compact connected abelian group) acts effectively on a compact space then the fixed point set is nonempty and H_G^*(X,Q) has a presentation similar to the presentation of H^*(X,Q) as proven by Chang in the case of a circle group.


Functionals Of Gasser--Muller Estimators, Petre Babilua, Elizbar Nadaraya, Grigol Sokhadze Jan 2014

Functionals Of Gasser--Muller Estimators, Petre Babilua, Elizbar Nadaraya, Grigol Sokhadze

Turkish Journal of Mathematics

The asymptotic properties of a general functional of the Gasser--Muller estimator are investigated in the Sobolev space. The convergence rate, consistency, and central limit theorem are established.


Oscillation Of Second Order Differential Equations With Mixed Nonlinearities, Zhiting Xu, Aijun Cheng Jan 2014

Oscillation Of Second Order Differential Equations With Mixed Nonlinearities, Zhiting Xu, Aijun Cheng

Turkish Journal of Mathematics

By refining the standard integral averaging technique, in this paper, new oscillation criteria as well as interval oscillation criteria are established for the second order delay differential equation with mixed nonlinearities \begin{equation*} (r(t) x^{\prime}(t) ^{\alpha-1}x^{\prime}(t))^{\prime}+q_0(t) x(\tau_0(t)) ^{\alpha-1}x(\tau_0(t)) +\sum\limits_{i = 1}^nq_i(t) x(\tau_i(t)) ^{\alpha_i-1}x(\tau_i(t)) = 0, \end{equation*} where \alpha>0, \alpha_i>0, i = 1,2,\cdots,n. Our results generalize and improve the known results in the literature. Examples are also given to illustrate the importance of our results.


Semi-Cotangent Bundle And Problems Of Lifts, Furkan Yildirim, Arif Salimov Jan 2014

Semi-Cotangent Bundle And Problems Of Lifts, Furkan Yildirim, Arif Salimov

Turkish Journal of Mathematics

Using the fiber bundle M over a manifold B, we define a semi-cotangent (pull-back) bundle t^{\ast}B, which has a degenerate symplectic structure. We consider lifting problem of projectable geometric objects on M to the semi-cotangent bundle. Relations between lifted objects and a degenerate symplectic structure are also presented.


On Generalized Robertson--Walker Spacetimes Satisfying Some Curvature Condition, Kadri̇ Arslan, Ryszard Deszcz, Ridvan Ezentaş, Marian Hotlos, Cengi̇zhan Murathan Jan 2014

On Generalized Robertson--Walker Spacetimes Satisfying Some Curvature Condition, Kadri̇ Arslan, Ryszard Deszcz, Ridvan Ezentaş, Marian Hotlos, Cengi̇zhan Murathan

Turkish Journal of Mathematics

We give necessary and sufficient conditions for warped product manifolds (M,g), of dimension \geqslant 4, with 1-dimensional base, and in particular, for generalized Robertson--Walker spacetimes, to satisfy some generalized Einstein metric condition. Namely, the difference tensor R . C - C . R, formed from the curvature tensor R and the Weyl conformal curvature tensor C, is expressed by the Tachibana tensor Q(S,R) formed from the Ricci tensor S and R. We also construct suitable examples of such manifolds. They are quasi-Einstein, i.e. at every point of M rank (S - \alpha g) \leqslant 1, for some \alpha \in R, …


Some Rings For Which The Cosingular Submodule Of Every Module Is A Direct Summand, Derya Keski̇n Tütüncü, Ni̇l Orhan Ertaş, Patrick F. Smith, Rachid Tribak Jan 2014

Some Rings For Which The Cosingular Submodule Of Every Module Is A Direct Summand, Derya Keski̇n Tütüncü, Ni̇l Orhan Ertaş, Patrick F. Smith, Rachid Tribak

Turkish Journal of Mathematics

The submodule \overline{Z}(M) = \cap {N M/N is small in its injective hull} was introduced by Talebi and Vanaja in 2002. A ring R is said to have property (P) if \overline{Z}(M) is a direct summand of M for every R-module M. It is shown that a commutative perfect ring R has (P) if and only if R is semisimple. An example is given to show that this characterization is not true for noncommutative rings. We prove that if R is a commutative ring such that the class {M \in Mod-R \overline{Z}_{R}(M) = 0} is closed under factor modules, then …


Half-Lightlike Submanifolds With Planar Normal Sections In R_2^4, Feyza Esra Erdoğan, Rifat Güneş, Bayram Şahi̇n Jan 2014

Half-Lightlike Submanifolds With Planar Normal Sections In R_2^4, Feyza Esra Erdoğan, Rifat Güneş, Bayram Şahi̇n

Turkish Journal of Mathematics

We investigate half-lightlike submanifolds with planar normal sections of 4-dimensional pseudo-Euclidean space. We obtain necessary and sufficient conditions for a half-lightlike submanifold of R_2^4 such that it has degenerate or nondegenerate planar normal sections.


\Xi^{\Perp}-Submanifolds Of Para-Sasakian Manifolds, Selcen Yüksel Perktaş, Mukut Mani Tripathi, Erol Kiliç, Sadik Keleş Jan 2014

\Xi^{\Perp}-Submanifolds Of Para-Sasakian Manifolds, Selcen Yüksel Perktaş, Mukut Mani Tripathi, Erol Kiliç, Sadik Keleş

Turkish Journal of Mathematics

Almost semiinvariant \xi^{\perp}-submanifolds of an almost paracontact metric manifold are defined and studied. Some characterizations of almost semiinvariant \xi^{\perp}-submanifolds and semiinvariant \xi^{\perp}-submanifolds are presented. A para-CR-structure is defined and it is proven that an almost semiinvariant \xi^{\perp}-submanifold of a normal almost paracontact metric (and hence para-Sasakian) manifold with the proper invariant distribution always possesses a para-\textit{CR}-structure. A counter example is also given. Integrability conditions for certain natural distributions arising on almost semiinvariant \xi^{\perp} -submanifolds are obtained. Finally, certain parallel operators on submanifolds are investigated.


On The Continued Fraction Expansion Of Some Hyperquadratic Functions, Khalil Ayadi, Fatma Taktak Jan 2014

On The Continued Fraction Expansion Of Some Hyperquadratic Functions, Khalil Ayadi, Fatma Taktak

Turkish Journal of Mathematics

In this paper, we consider continued fraction expansions for algebraic power series over a finite field. Especially, we are interested in studying the continued fraction expansion of a particular subset of algebraic power series over a finite field, called hyperquadratic. This subset contains irrational elements \alpha satisfying an equation \alpha = f(\alpha^r), where r is a power of the characteristic of the base field and f is a linear fractional transformation with polynomials coefficients. The continued fraction expansion for these elements can sometimes be given fully explicitly. We will show this expansion for hyperquadratic power series satisfying certain types of …


Monomial Ideals Of Linear Type, Monica La Barbiera, Paola Lea Stagliano' Jan 2014

Monomial Ideals Of Linear Type, Monica La Barbiera, Paola Lea Stagliano'

Turkish Journal of Mathematics

Let S=K[x_1,…,x_n;y_1,…,y_m] be the polynomial ring in 2 sets of variables over a field K. We investigate some classes of monomial ideals of S in order to classify ideals of the linear type.


Two-Weighted Norm Inequality On Weighted Morrey Spaces, Xiaofeng Ye, Tengfei Wang Jan 2014

Two-Weighted Norm Inequality On Weighted Morrey Spaces, Xiaofeng Ye, Tengfei Wang

Turkish Journal of Mathematics

Let u and \omega be weight functions. We shall introduce the weighted Morrey spaces L^{p,\kappa} (\omega) and investigate the sufficient condition and necessary condition about the 2-weighted boundedness of the Hardy--Littlewood maximal operator.


On Density Theorems For Rings Of Krull Type With Zero Divisors, Başak Ay Saylam Jan 2014

On Density Theorems For Rings Of Krull Type With Zero Divisors, Başak Ay Saylam

Turkish Journal of Mathematics

Let R be a commutative ring and I(R) denote the multiplicative group of all invertible fractional ideals of R, ordered by A \leqslant B if and only if B \subseteq A. If R is a Marot ring of Krull type, then R_{(P_i)}, where {P_i}_{i \in I} are a collection of prime regular ideals of R, is a valuation ring and R = \bigcap R_{(P_i)}. We denote by G_i the value group of the valuation associated with R_{(P_i)}. We prove that there is an order homomorphism from I(R) into the cardinal direct sum \coprod_{i \in I} G_i and we investigate the …


Degenerate Hopf Bifurcations, Hidden Attractors, And Control In The Extended Sprott E System With Only One Stable Equilibrium, Zhouchao Wei, Irene Moroz, Anping Liu Jan 2014

Degenerate Hopf Bifurcations, Hidden Attractors, And Control In The Extended Sprott E System With Only One Stable Equilibrium, Zhouchao Wei, Irene Moroz, Anping Liu

Turkish Journal of Mathematics

In this paper, we introduce an extended Sprott E system by a general quadratic control scheme with 3 arbitrary parameters for the new system. The resulting system can exhibit codimension-one Hopf bifurcations as parameters vary. The control strategy used can be applied to create degenerate Hopf bifurcations at desired locations with preferred stability. A complex chaotic attractor with only one stable equilibrium is derived in the sense of having a positive largest Lyapunov exponent. The chaotic attractor with only one stable equilibrium can be generated via a period-doubling bifurcation. To further suppress chaos in the extended Sprott E system coexisting …


Seiberg--Witten-Like Equations On 5-Dimensional Contact Metric Manifolds, Nedi̇m Deği̇rmenci̇, Şenay Bulut Jan 2014

Seiberg--Witten-Like Equations On 5-Dimensional Contact Metric Manifolds, Nedi̇m Deği̇rmenci̇, Şenay Bulut

Turkish Journal of Mathematics

In this paper, we write Seiberg--Witten-like equations on contact metric manifolds of dimension 5. Since any contact metric manifold has a Spin^c-structure, we use the generalized Tanaka--Webster connection on a Spin^c spinor bundle of a contact metric manifold to define the Dirac-type operators and write the Dirac equation. The self-duality of 2-forms needed for the curvature equation is defined by using the contact structure. These equations admit a nontrivial solution on 5-dimensional strictly pseudoconvex CR manifolds whose contact distribution has a negative constant scalar curvature.


On 4-Dimensional Almost Para-Complex Pure-Walker Manifolds, Murat İşcan, Hi̇lmi̇ Sarsilmaz, Si̇bel Turanli Jan 2014

On 4-Dimensional Almost Para-Complex Pure-Walker Manifolds, Murat İşcan, Hi̇lmi̇ Sarsilmaz, Si̇bel Turanli

Turkish Journal of Mathematics

This paper is concerned with almost para-complex structures on Walker 4-manifolds. For these structures, we study some problems of Kähler manifolds. We also give an example of a flat almost para-complex manifold, which consists of a nonintegrable almost para-complex structure on Walker 4-manifolds.


On The Nilpotent Graph Of A Ring, Mohammad Javad Nikmehr, Soheila Khojasteh Jan 2013

On The Nilpotent Graph Of A Ring, Mohammad Javad Nikmehr, Soheila Khojasteh

Turkish Journal of Mathematics

Let R be a ring with unity. The nilpotent graph of R, denoted by \Gamma_N(R), is a graph with vertex set Z_N(R)^* = {0 \neq x \in R \mid xy \in N(R) for some 0 \neq y \in R}; and two distinct vertices x and y are adjacent if and only if xy \in N(R), where N(R) is the set of all nilpotent elements of R. Recently, it has been proved that if R is a left Artinian ring, then diam(\Gamma_N(R)) \leq 3. In this paper, we present a new proof for the above result, where R is a finite …


On The Centroid Of Prime Semirings, Hasret Yazarli, Mehmet Ali̇ Öztürk Jan 2013

On The Centroid Of Prime Semirings, Hasret Yazarli, Mehmet Ali̇ Öztürk

Turkish Journal of Mathematics

We define and study the extended centroid of a prime semiring. We show that the extended centroid is a semifield and give some properties of the centroid of a right multiplicatively cancellable prime semiring.


Products Of Conjugacy Classes And Products Of Irreducible Characters In Finite Groups, Mohammad Reza Darafsheh, Sajjad Mahmood Robati Jan 2013

Products Of Conjugacy Classes And Products Of Irreducible Characters In Finite Groups, Mohammad Reza Darafsheh, Sajjad Mahmood Robati

Turkish Journal of Mathematics

Let G be a finite group. If A and B are two conjugacy classes in G, then AB is a union of conjugacy classes in G and \eta(AB) denotes the number of distinct conjugacy classes of G contained in AB. If \chi and \psi are two complex irreducible characters of G, then \chi\psi is a character of G and again we let \eta(\chi\psi) be the number of irreducible characters of G appearing as constituents of \chi\psi. In this paper our aim is to study the product of conjugacy classes in a finite group and obtain an upper bound for \eta …


Global Existence, Decay And Blow Up Solutions For Coupled Nonlinear Wave Equations With Damping And Source Terms, Erhan Pi̇şki̇n, Necat Polat Jan 2013

Global Existence, Decay And Blow Up Solutions For Coupled Nonlinear Wave Equations With Damping And Source Terms, Erhan Pi̇şki̇n, Necat Polat

Turkish Journal of Mathematics

We study the initial-boundary value problem for a system of nonlinear wave equations with nonlinear damping and source terms, in a bounded domain. The decay estimates of the energy function are established by using Nakao's inequality. The nonexistence of global solutions is discussed under some conditions on the given parameters.


Bbm Equation With Non-Constant Coefficients, Amutha Senthilkumar Jan 2013

Bbm Equation With Non-Constant Coefficients, Amutha Senthilkumar

Turkish Journal of Mathematics

In this article, a model for the propagation of long waves over an uneven bottom is considered. We provide both theoretical and numerical results for this model. We also discuss the changes which occur in a solitary wave solution of the BBM equation as it travels through a channel of decreasing depth.