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2019

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Articles 991 - 1020 of 1389

Full-Text Articles in Mathematics

On Strongly Ozaki Bi-Close-To-Convex Functions, Münevver Tezelci̇, Sevtap Sümer Eker Jan 2019

On Strongly Ozaki Bi-Close-To-Convex Functions, Münevver Tezelci̇, Sevtap Sümer Eker

Turkish Journal of Mathematics

In this paper, we introduce and investigate a new subclass of strongly Ozaki bi-close-to-convex functions in the open unit disk. We have also found estimates for the first two Taylor-Maclaurin coefficients for functions belonging to this class. The results presented in this paper have been shown to generalize and improve the work of Brannan and Taha.

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Inverse Problem For Sturm-Liouville Differential Operators With Two Constant Delays, Mohammad Shahriari Jan 2019

Inverse Problem For Sturm-Liouville Differential Operators With Two Constant Delays, Mohammad Shahriari

Turkish Journal of Mathematics

In this manuscript, we study nonself-adjoint second-order differential operators with two constant delays. We investigate the properties of the spectral characteristics and the inverse problem of recovering operators from their spectra. An inverse spectral problem is studied of recovering the potential from spectra of two boundary value problems with one common boundary condition. The uniqueness theorem is proved for this inverse problem.

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Fuzzy Soft Topological Spaces And The Related Category Fst, Tuğba Han Şi̇mşekler Jan 2019

Fuzzy Soft Topological Spaces And The Related Category Fst, Tuğba Han Şi̇mşekler

Turkish Journal of Mathematics

In this paper, we consider fuzzy soft sets with a different approach where we generalize the idea initially introduced by \v{S}ostak for fuzzy sets. Subsequently, we define the fuzzy set topology categories of fuzzy soft topological spaces and give certain properties of them. Furthermore, we define the initial and the final fuzzy soft topological spaces.

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Global Dynamics Of Perturbation Of Certain Rational Differenceequation, Sabina Hrustic, Mustafa Kulenovic, Samra Moranjkic, Zehra Nurkanovic Jan 2019

Global Dynamics Of Perturbation Of Certain Rational Differenceequation, Sabina Hrustic, Mustafa Kulenovic, Samra Moranjkic, Zehra Nurkanovic

Turkish Journal of Mathematics

We investigate the global asymptotic stability of the difference equation of the form \begin{equation*} x_{n+1}=\frac{A x_{n}^{2}+F}{a x_{n}^{2}+e x_{n-1}}, \quad n=0,1,\ldots, \end{equation*}% with positive parameters and nonnegative initial conditions such that $x_0 + x_{-1}>0$. The map associated to this equation is always decreasing in the second variable and can be either increasing or decreasing in the first variable depending on the parametric space. In some cases, we prove that local asymptotic stability of the unique equilibrium point implies global asymptotic stability.

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Additive Derivative And Multiplicative Coderivative Operators On Mv-Algebras, Ahmet Hamal Jan 2019

Additive Derivative And Multiplicative Coderivative Operators On Mv-Algebras, Ahmet Hamal

Turkish Journal of Mathematics

In this paper we introduce derivative MV-algebras (or MV-algebras with additive derivative operators). We indicate that the derivative MV-algebras are generalizations of closure MV-algebras. Then we investigate the connection between additive derivative operators on MV-algebras and the derivative operators on the greatest Boolean subalgebras of MV-algebras. Finally, we study some properties of the derivative MV-algebras.

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On Band Operators, Bahri̇ Turan, Kazim Özcan Jan 2019

On Band Operators, Bahri̇ Turan, Kazim Özcan

Turkish Journal of Mathematics

Let $G$ and $H$ be Archimedean Riesz spaces. We study the properties of band operators and inverse band operators from $G$ to $H$ and investigate their relations to some well-known classes of operators. Then, we show that under some assumptions on the Riesz spaces $G$ or $H$, if $S$ is a bijective band operator from $G$ into $H$ then $S^{-1}:H\rightarrow G$ is a band operator. Additionally, we give some conditions under which a band operator becomes order bounded.

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Coefficient Bounds And Distortion Theorems For The Certain Analytic Functions, Osman Altintaş, Ni̇zami̇ Mustafa Jan 2019

Coefficient Bounds And Distortion Theorems For The Certain Analytic Functions, Osman Altintaş, Ni̇zami̇ Mustafa

Turkish Journal of Mathematics

In this paper, we introduce and investigate an analytic function class $% P_{q}(\lambda,A,B)$ that we call the class of $q-$starlike and $q-$convex functions with respect to the parameter $\lambda $. We give coefficient bounds estimates, distortion bound and growth theorems for the functions belonging to this class.

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On The Divisors Of Shifted Primes, Jean Marie De Koninck, Imre Katai Jan 2019

On The Divisors Of Shifted Primes, Jean Marie De Koninck, Imre Katai

Turkish Journal of Mathematics

Let $\tau(n)$ stand for the number of positive divisors of $n$. Given an additive function $f$ and a real number $\alpha\in [0,1)$, let $\displaystyle{h_n(\alpha):= \frac 1{\tau(n)} \sum_{d\mid n \atop \{f(d)\}

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Study On The Existence Of Solutions To Two Specific Types Of Differential-Difference Equations, Qiong Wang, Qiongyan Wang Jan 2019

Study On The Existence Of Solutions To Two Specific Types Of Differential-Difference Equations, Qiong Wang, Qiongyan Wang

Turkish Journal of Mathematics

This paper concerns the description of the entire or meromorphic solutions to two certain types of differential-difference equations under some certain conditions. The significance of our results lies in that we find the entire solutions of the second type equation with the form $f=Ae^{Bz}$, where $A,B$ are constants that are completely determined only by coefficients and correlated indices. Our results are accurate in a certain sense and are supplemented by an example. In particular, our results generalize and improve a result of Zhang and Huang, and they are closely related to recent results by Dong and Liao.

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On Near Soft Sets, Alkan Özkan Jan 2019

On Near Soft Sets, Alkan Özkan

Turkish Journal of Mathematics

This study aims to contribute to the theoretical studies on near soft sets and near soft topological spaces. In addition, it presents basic concepts and constructs that will form the basis for a near theoretical set-up of near soft sets. These concepts and structures include near soft point, near soft interior, near soft closure, near soft neighborhood, near soft continuity, and near soft open (closed) function.

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Fatou, Julia, And Escaping Sets In Holomorphic (Sub)Semigroup Dynamics, Bishnu Hari Subedi, Ajaya Singh Jan 2019

Fatou, Julia, And Escaping Sets In Holomorphic (Sub)Semigroup Dynamics, Bishnu Hari Subedi, Ajaya Singh

Turkish Journal of Mathematics

We investigate under what conditions the Fatou, Julia, and escaping sets of a transcendental semigroup are respectively equal to the Fatou, Julia, and escaping sets of their subsemigroups. We define the partial fundamental set and fundamental set of a holomorphic semigroup, and on the basis of these sets, we prove that the Fatou and escaping sets of a transcendental semigroup $ S $ are nonempty.

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The Numerical Range Of Matrices Over $\Mathbb {F}_4$, Edoardo Ballico Jan 2019

The Numerical Range Of Matrices Over $\Mathbb {F}_4$, Edoardo Ballico

Turkish Journal of Mathematics

For any prime power $q$ and any $u = (x_1,\dots ,x_n),v = (y_1,\dots ,y_n)\in \mathbb {F} _{q^2}^n$ set $\langle u,v\rangle := \sum _{i=1}^{n} x_i^qy_i$. For any $k\in \mathbb {F} _q$ and any $n\times n$ matrix $M$ over $\mathbb {F} _{q^2}$, the $k$-numerical range $\mathrm{Num} _k(M)$ of $M$ is the set of all $\langle u,Mu\rangle$ for $u\in \mathbb {F} _{q^2}^n$ with $\langle u,u\rangle =k$ \cite{cjklr}. Here, we study the case $q=2$, which is quite different from the case $q\ne 2$.

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Conformal Changes Of Generalized Paracontact Pseudometric Structures, Fereshteh Malek, Niloufar Hosseinpour Kashani Jan 2019

Conformal Changes Of Generalized Paracontact Pseudometric Structures, Fereshteh Malek, Niloufar Hosseinpour Kashani

Turkish Journal of Mathematics

We characterize generalized almost paracontact pseudometric structures after a conformal change and investigate invariant components of these structures under conformal changes. Then we characterize the conformal changes of normal generalized paracontact pseudometric structures, generalized almost para-co-K{\"a}hler structures, and generalized para-co-K{\"a}hler structures. We also give examples of a generalized almost para-co-K{\"a}hler structure and a normal generalized paracontact pseudometric structure that remains invariant under a nonhomothety conformal change.

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On S-Prime Submodules, Esra Şengelen Sevi̇m, Tarik Arabaci, Ünsal Teki̇r, Suat Koç Jan 2019

On S-Prime Submodules, Esra Şengelen Sevi̇m, Tarik Arabaci, Ünsal Teki̇r, Suat Koç

Turkish Journal of Mathematics

In this study, we introduce the concepts of $S$-prime submodules and\ $S$% -torsion-free modules, which are generalizations of prime submodules and torsion-free modules. Suppose $S\subseteq R\ $is a multiplicatively closed subset of a commutative ring$\ R$, and let $M$ be a unital $R$-module. A submodule $P\ $of $M\ $with $(P:_{R}M)\cap S=\emptyset$ is called an $S$% -prime submodule if there is an $s\in S$\ such that $am\in P$ implies $% sa\in(P:_{R}M)\ $or $sm\in P.\ $Also, an $R$-module $M\ $is called $S$% -torsion-free if $ann(M)\cap S=\emptyset$ and there exists $s\in S\ $such that $am=0\ $implies $sa=0\ $or $sm=0\ $for each $a\in R\ …

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A Class Of Finite Difference Schemes For Singularly Perturbed Delay Differential Equations Of Second Order, Pramod Chakravarthy Podila, Kamalesh Kumar Jan 2019

A Class Of Finite Difference Schemes For Singularly Perturbed Delay Differential Equations Of Second Order, Pramod Chakravarthy Podila, Kamalesh Kumar

Turkish Journal of Mathematics

In this paper, we proposed a new class of finite difference schemes for solving singularly perturbed delay differential equation of second order. The proposed schemes are oscillation-free and more accurate than conventional schemes on a uniform mesh. These schemes are easily adaptable on special meshes like Shishkin mesh or Bakhvalov mesh and are uniformly convergent with respect to the perturbation parameter. The error analysis has been carried out and numerical examples are presented to show the accuracy and efficiency of the proposed schemes.

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Quantum Integral Equations Of Volterra Type In Terms Of Discrete-Time Normal Martingale, Jinshu Chen, Yuling Tang Jan 2019

Quantum Integral Equations Of Volterra Type In Terms Of Discrete-Time Normal Martingale, Jinshu Chen, Yuling Tang

Turkish Journal of Mathematics

In this paper, we aim to introduce a quantum linear stochastic Volterra integral equation of convolution type with operator-valued kernels in a nuclear topological algebra. We first establish the existence and uniqueness of the solutions and give the explicit expression of the solutions. Then we prove the continuity, continuous dependence on free terms and other properties of the solution.

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Numerical Solutions Of Black-Scholesintegro-Differential Equations With Convergenceanalysis, Azim Rivaz, Mahmoud Mohseni Moghadam, Samaneh Baniasadi Jan 2019

Numerical Solutions Of Black-Scholesintegro-Differential Equations With Convergenceanalysis, Azim Rivaz, Mahmoud Mohseni Moghadam, Samaneh Baniasadi

Turkish Journal of Mathematics

Stochastic integro-differential equations are obtained when we consider prices jump in financial modelling. In this paper, these equations are solved numerically by applying the two-dimensional Tau method with ordinary bases. Next, the numerical solutions of the equations above are investigated by the ordinary bases to the Hermitian one. Moreover, we provide an error analysis for the Tau method with ordinary bases. Also, we will prove that the errors of the approximate solutions decay exponentially in weighted ${L^{2}}$-norm. At the end, we will provide some numerical examples which show the efficiency and accuracy of the method.

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Some Unpublished Reclaw Theorems And Their Applications To Baire-Star-One Functions, Tomasz Natkaniec, Waldemar Sieg Jan 2019

Some Unpublished Reclaw Theorems And Their Applications To Baire-Star-One Functions, Tomasz Natkaniec, Waldemar Sieg

Turkish Journal of Mathematics

Lunina's 7-tuples $\langle E^1,\ldots, E^7\rangle$ of sets of pointwise convergence, divergence to $\infty$, divergence to $-\infty$, etc. for sequences of Baire-star-one functions are cha\-racterized. Generalization on ideal convergence of such sequences is discussed. Limits and ideal limits of sequences of Baire-star-one functions are considered in the last part of the article.

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$\Alpha$-Associated Metrics On Rigged Null Hypersurfaces, Ferdinand Ngakeu, Hans Fotsing Tetsing Jan 2019

$\Alpha$-Associated Metrics On Rigged Null Hypersurfaces, Ferdinand Ngakeu, Hans Fotsing Tetsing

Turkish Journal of Mathematics

Let $x:(M,g)\to(\Bm,\bg)$ be a null hypersurface isometrically immersed into a proper semi-Riemannian manifold $(\overline{M},\bar g)$. A rigging for $M$ is a vector field $\zeta$ defined on some open subset of $\overline{M}$ containing $M$ such that $\zeta_p\notin T_pM$ for every $p\in M$. Such a vector field induces an everywhere transversal null vector field $N$ defined over $M$ and which induces on $M$ the same geometrical objects as $\zeta$. Let $\bar \eta$ be the 1-form that is $\bar g$-metrically equivalent to $N$ and let $\eta=x^\star\bar\eta$ be its pullback on $M$. For a given nowhere vanishing smooth function $\alpha$ on $M$, we have …

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On Isotropic Projective Ricci Curvature Of C-Reducible Finsler Metrics, Laya Ghaemnezhad, Bahman Rezaei, Mehran Gabrani Jan 2019

On Isotropic Projective Ricci Curvature Of C-Reducible Finsler Metrics, Laya Ghaemnezhad, Bahman Rezaei, Mehran Gabrani

Turkish Journal of Mathematics

Projective Ricci curvature is a projective invariant quantity in Finsler geometry which is introduced by Z. Shen. In this paper, we study special projective Ricci curvature of C-reducible Finsler metrics. The necessary and sufficient conditions of these metrics, which cause these metrics to be weak or isotropic projective Ricci curvature, are found and it is proved that C-reducible Douglas metric of isotropic PRic-curvature must be PRic flat. The same theorem for C-reducible metrics of scalar flag curvature is also investigated.

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Some Ergodic Properties Of Multipliers On Commutative Banach Algebras, Heybetkulu Mustafayev, Hayri̇ Topal Jan 2019

Some Ergodic Properties Of Multipliers On Commutative Banach Algebras, Heybetkulu Mustafayev, Hayri̇ Topal

Turkish Journal of Mathematics

A commutative semisimple regular Banach algebra $A$ with the Gelfand space $ \Sigma _{A}$ is called a Ditkin algebra if each point of $\Sigma _{A}\cup \left\{ \infty \right\} $ is a set of synthesis for $A$. Generalizing the Choquet-Deny theorem, it is shown that if $T$ is a multiplier of a Ditkin algebra $A,$ then $\left\{ \varphi \in A^{\ast }:T^{\ast }\varphi =\varphi \right\} $ is finite dimensional if and only if \textnormal{card}$\mathcal{F}_{T}$ is finite, where $\mathcal{F}_{T}=\left\{ \gamma \in \Sigma _{A}:\widehat{T}\left( \gamma \right) =1\right\} $ and $ \widehat{T}$ is the Helgason-Wang representation of $T.$

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Perfect Numerical Semigroups, María Ángeles Moreno Frías, Jose Carlos Rosales Jan 2019

Perfect Numerical Semigroups, María Ángeles Moreno Frías, Jose Carlos Rosales

Turkish Journal of Mathematics

A numerical semigroup is perfect if it does not have isolated gaps. In this paper we will order the perfect numerical semigroups with a fixed multiplicity. This ordering allows us to give an algorithm procedure to obtain them. We also study the perfect monoid, which is a subset of $\N$ that can be expressed as an intersection of perfect numerical semigroups, and we present the perfect monoid generated by a subset of $\N$. We give an algorithm to calculate it. We study the perfect closure of a numerical semigroup, as well as the perfect numerical semigroup with maximal embedding dimension, …

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On Positive Periodic Solutions Of Second-Order Semipositonedifferential Equations, Fanglei Wang, Nannan Yang Jan 2019

On Positive Periodic Solutions Of Second-Order Semipositonedifferential Equations, Fanglei Wang, Nannan Yang

Turkish Journal of Mathematics

Using the Krasnosel'skii's fixed point theorem, we establish the existence and multiplicity of positive $\mathrm{T}$-periodic solutions of second-order semipositone system $ \left \{\begin{array}{lcr} x''(t)+a(t)x(t)=\lambda f(t,x(t)),\\ x(0)=x(\mathrm{T}),x'(0)=x'(\mathrm{T}), \end{array}\right. $ where $x=(x_1,x_2,\cdots,x_n)$, $f(t,x)=(f_1(t,x),f_2(t,x),\cdots,f_n(t,x))$ is bounded below.

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A Blow-Up Result For Nonlocal Thin-Film Equation With Positive Initial Energy, Mustafa Polat Jan 2019

A Blow-Up Result For Nonlocal Thin-Film Equation With Positive Initial Energy, Mustafa Polat

Turkish Journal of Mathematics

In this note, we consider a thin-film equation including a diffusion term, a fourth order term and a nonlocal source term under the periodic boundary conditions. In particular, a finite time blow-up result is established for the case of positive initial energy provided that \[ \frac{\pi^2}{a^2}\leq \frac{2}{p-1},\] where $a$ is the length of the interval and $p>1$ is the power of nonlinear force term. Also upper and lower blow-up times are estimated.

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Solvability Of A System Of Nonlinear Difference Equations Of Higher Order, Merve Kara, Yasi̇n Yazlik Jan 2019

Solvability Of A System Of Nonlinear Difference Equations Of Higher Order, Merve Kara, Yasi̇n Yazlik

Turkish Journal of Mathematics

In this paper, we show that the following higher-order system of nonlinear difference equations, $ x_{n}=\frac{x_{n-k}y_{n-k-l}}{y_{n-l}\left( a_{n}+b_{n}x_{n-k}y_{n-k-l}\right)}, \ y_{n}=\frac{y_{n-k}x_{n-k-l}}{x_{n-l}\left( \alpha_{n}+\beta_{n}y_{n-k}x_{n-k-l}\right)}, \ n\in \mathbb{N}_{0}, $ where $k,l\in \mathbb{N}$, $\left(a_{n} \right)_{n\in \mathbb{N}_{0}}, \left(b_{n} \right)_{n\in \mathbb{N}_{0}}, \left(\alpha_{n} \right)_{n\in \mathbb{N}_{0}}, \left(\beta_{n} \right)_{n\in \mathbb{N}_{0}}$ and the initial values $x_{-i}, \ y_{-i}$, $i=\overline {1,k+l}$, are real numbers, can be solved and some results in the literature can be extended further. Also, by using these obtained formulas, we investigate the asymptotic behavior of well-defined solutions of the above difference equations system for the case $k=2, l=k$.

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Existence Resultsfor Some Neutral Functional Integrodifferential Equations With Bounded Delay, Sylvain Koumla, Radu Precup, Abdou Sene Jan 2019

Existence Resultsfor Some Neutral Functional Integrodifferential Equations With Bounded Delay, Sylvain Koumla, Radu Precup, Abdou Sene

Turkish Journal of Mathematics

In this paper, we study a class of neutral functional integrodifferential equations with finite delay in Banach spaces. We are interested in the global existence, uniqueness of mild solutions with values in the Banach space and in its subspace $D(A).$ The results are based on Banach's and Schauder's fixed point theorems and on the technique of equivalent norms. As an application, we consider a diffusion neutral functional integrodifferential equation.

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Trigonometric Expressions For Gaussian $_2f_1$-Series, Wenchang Chu Jan 2019

Trigonometric Expressions For Gaussian $_2f_1$-Series, Wenchang Chu

Turkish Journal of Mathematics

The classical Gaussian $_2F_1$-series containing two free variables $\{x,y\}$ and two integer parameters $\{m,n\}$ are investigated by the linearization method. Several closed formulae are derived in terms of trigonometric functions. Some of them are lifted up, via a trigonometric integral approach, to identities of nonterminating $_3F_2$-series.

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Cremona Transformations Of Plane Configurations Of 6 Points, Remzi̇ye Arzu Zabun Jan 2019

Cremona Transformations Of Plane Configurations Of 6 Points, Remzi̇ye Arzu Zabun

Turkish Journal of Mathematics

We analyze how a set of 6 points of $\Rp 2$ in general position changes under quadratic Cremona transformations based at triples of points of the given six. As an application, we give an alternative approach to determining the deformation types (i.e. icosahedral, bipartite, tripartite and hexagonal) of 36 real Schlafli double sixes on any nonsingular real cubic surface performed by Segre.

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On Surfaces Endowed With A Canonical Principal Direction In Euclidean 4-Spaces, Alev Kelleci̇, Nuretti̇n Cenk Turgay, Mahmut Ergüt Jan 2019

On Surfaces Endowed With A Canonical Principal Direction In Euclidean 4-Spaces, Alev Kelleci̇, Nuretti̇n Cenk Turgay, Mahmut Ergüt

Turkish Journal of Mathematics

In this paper, we introduce canonical principal direction (CPD) submanifolds with higher codimension in Euclidean spaces. Then we obtain a classification of surfaces endowed with CPD relative to a fixed direction in Euclidean 4-space.

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On Uniformly $Pr$-Ideals In Commutative Rings, Rabi̇a Nagehan Üregen Jan 2019

On Uniformly $Pr$-Ideals In Commutative Rings, Rabi̇a Nagehan Üregen

Turkish Journal of Mathematics

Let $R\ $be a commutative ring with nonzero identity and $I\ $a proper ideal of $R.\ $Then $I\ $is called a uniformly $pr$-ideal if there exists $N\in% \mathbb{N} $ such that $ab\in I\ $with $ann(a)=0\ $then $b^{N}\in I.\ $We say that the smallest $N\in% \mathbb{N} $ is called order of $I\ $and denoted by $ord_{R}(I)=N.\ $In this paper, we give some examples and characterizations of this new class of ideals.

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