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Full-Text Articles in Physical Sciences and Mathematics

Approximate Groups Iii: The Unitary Case, Emmanuel Breuillard, Ben Green Jan 2012

Approximate Groups Iii: The Unitary Case, Emmanuel Breuillard, Ben Green

Turkish Journal of Mathematics

By adapting the classical proof of Jordan's theorem on finite subgroups of linear groups, we show that every approximate subgroup of the unitary group U_n(C) is almost abelian.


Groupoids, Imaginaries And Internal Covers, Ehud Hrushovski Jan 2012

Groupoids, Imaginaries And Internal Covers, Ehud Hrushovski

Turkish Journal of Mathematics

Let T be a first-order theory. A correspondence is established between internal covers of models of T and definable groupoids within T. We also consider amalgamations of independent diagrams of algebraically closed substructures, and find strong relation between covers, uniqueness for 3-amalgamation, existence of 4-amalgamation, imaginaries of T^\si, and definable groupoids. As a corollary, we describe the imaginary elements of families of finite-dimensional vector spaces over pseudo-finite fields.


On \Alpha-Skew Mccoy Modules, Jian Cui, Jianlong Chen Jan 2012

On \Alpha-Skew Mccoy Modules, Jian Cui, Jianlong Chen

Turkish Journal of Mathematics

Let \alpha be a ring endomorphism. Extending the notions of McCoy modules and \alpha-skew McCoy rings, we introduce the notion of \alpha-skew McCoy modules, which can also be regarded as a generalization of \alpha-skew Armendariz modules. A number of illustrative examples are given. Various properties of these modules are developed, and equivalent conditions for \alpha-skew McCoy modules are established. Furthermore, we study the relationship between a module and its polynomial module.


On Some New Inequalities For Convex Functions, Mevlüt Tunç Jan 2012

On Some New Inequalities For Convex Functions, Mevlüt Tunç

Turkish Journal of Mathematics

In the present paper we establish some new integral inequalities analogous to the well known Hadamard's inequality by using a fairly elementary analysis.


An Oscillation Theorem For Second-Order Nonlinear Differential Equations Of Euler Type, Asadollah Aghajani, Vahid Roomi Jan 2012

An Oscillation Theorem For Second-Order Nonlinear Differential Equations Of Euler Type, Asadollah Aghajani, Vahid Roomi

Turkish Journal of Mathematics

We consider the nonlinear equation t^2x'' + g(x) = 0, where g(x) satisfies xg(x) > 0 for x \ne 0, but is not assumed to be sublinear or superlinear. We study the problem whether all nontrivial solutions of the equation are oscillatory in some critical cases.


A Generalization Of Banach's Contraction Principle For Some Non-Obviously Contractive Operators In A Cone Metric Space, Yingxin Guo Jan 2012

A Generalization Of Banach's Contraction Principle For Some Non-Obviously Contractive Operators In A Cone Metric Space, Yingxin Guo

Turkish Journal of Mathematics

This paper investigates the fixed points for self-maps of a closed set in a space of abstract continuous functions. Our main results essentially extend and generalize some fixed point theorems in cone metric spaces. An application to differential equations is given.


Marcinkiewicz-Fejer Means Of Double Conjugate Walsh-Kaczmarz-Fourier Series And Hardy Spaces, Ushangi Goginava, Karoly Nagy Jan 2012

Marcinkiewicz-Fejer Means Of Double Conjugate Walsh-Kaczmarz-Fourier Series And Hardy Spaces, Ushangi Goginava, Karoly Nagy

Turkish Journal of Mathematics

In the present paper we prove that for any 0 < p \leq 2/3 there exists a martingale f in H_p such that the Marcinkiewicz-Fejér means of double conjugate Walsh-Kaczmarz-Fourier series of the martingale f is not uniformly bounded in the space L_p.


Geodesicity And Isoclinity Properties For The Tangent Bundle Of The Heisenberg Manifold With Sasaki Metric, Simona Luiza Druta, Paola Piu Jan 2012

Geodesicity And Isoclinity Properties For The Tangent Bundle Of The Heisenberg Manifold With Sasaki Metric, Simona Luiza Druta, Paola Piu

Turkish Journal of Mathematics

We prove that the horizontal and vertical distributions of the tangent bundle with the Sasaki metric are isocline, the distributions given by the kernels of the horizontal and vertical lifts of the contact form \omega on the Heisenberg manifold (H_3,g) to (TH_3,g^S) are not totally geodesic, and the distributions F^H=L(E_1^H,E_2^H) and F^V=L(E_1^V,E_2^V) are totally geodesic, but they are not isocline. We obtain that the horizontal and natural lifts of the curves from the Heisenberg manifold (H_3,g), are geodesics on the tangent bundle endowed with the Sasaki metric (TH_3,g^s), if and only if the curves considered on the base manifold are …


Best Simultaneous Approximation In Function And Operator Spaces, Eyad Abu-Sirhan Jan 2012

Best Simultaneous Approximation In Function And Operator Spaces, Eyad Abu-Sirhan

Turkish Journal of Mathematics

Let Z be a Banach space and G be a closed subspace of Z. For f_1,f_2 \in Z, the distance from f_1,f_2 to G is defined by d(f_1,f_2,G) = \underset{f \in G}{\inf} max { f_1-f , f_2-f }. An element g^{\ast} \in G satisfying max { f_1-g^{\ast } , f_2-g^{\ast } } = \underset{f \in G}{\inf } max { f_1-f , f_2-f } is called a best simultaneous approximation for f_1,f_2 from G. In this paper, we study the problem of best simultananeous approximation in the space of all continuous X-valued functions on a compact Hausdorff space S; C(S,X), and …


Small Covers Over Products Of A Polygon With A Simplex, Yanying Wang, Yanchang Chen Jan 2012

Small Covers Over Products Of A Polygon With A Simplex, Yanying Wang, Yanchang Chen

Turkish Journal of Mathematics

The equivariant homeomorphism class of an (orientable) small cover over a simple convex polytope P^n bijectively corresponds to the equivalence class of its (orientable) coloring under the action of automorphism group of face poset of P^n. By calculating the number of orbits of group actions we determine the number of equivariant homeomorphism classes of small covers over products of a polygon with a simplex. Moreover, we calculate the number of equivariant homeomorphism classes of all orientable small covers over the product.


Contact Cr-Warped Product Submanifolds In Generalized Sasakian Space Forms, Si̇bel Sular, Ci̇han Özgür Jan 2012

Contact Cr-Warped Product Submanifolds In Generalized Sasakian Space Forms, Si̇bel Sular, Ci̇han Özgür

Turkish Journal of Mathematics

We consider a contact CR-warped product submanifold M=M_{\top} \times_fM_{\bot} of a trans-Sasakian generalized Sasakian space form \widetilde{M} (f_1,f_2,f_3). We show that M is a contact CR-product under certain conditions.


Best Constants In Second-Order Sobolev Inequalities On Compact Riemannian Manifolds In The Presence Of Symmetries, Mohammed Ali Jan 2012

Best Constants In Second-Order Sobolev Inequalities On Compact Riemannian Manifolds In The Presence Of Symmetries, Mohammed Ali

Turkish Journal of Mathematics

Let (M,g) be a smooth compact 3\leq n-dimensional Riemannian manifold, and G a subgroup of the isometry group of (M,g). We establish the best constants in second-order for a Sobolev inequality when the functions are G-invariant.


Flat Surfaces In The Minkowski Space E^3_1 With Pointwise 1-Type Gauss Map, Uğur Dursun, Emel Coşkun Jan 2012

Flat Surfaces In The Minkowski Space E^3_1 With Pointwise 1-Type Gauss Map, Uğur Dursun, Emel Coşkun

Turkish Journal of Mathematics

In this article, we obtain all nonplanar cylindrical surfaces in the Minkowski space E^3_1 with pointwise 1-type Gauss map of the second kind. We also prove that right circular cones and hyperbolic cones in E^3_1 are the only cones in E^3_1 with pointwise 1-type Gauss map of the second kind. We conclude that there is no tangent developable surface fully lying in E^3_1 with pointwise 1-type Gauss map of the second kind.


An Identity Between The M-Spotty Weight Enumerators Of A Linear Code And Its Dual, İrfan Şi̇ap Jan 2012

An Identity Between The M-Spotty Weight Enumerators Of A Linear Code And Its Dual, İrfan Şi̇ap

Turkish Journal of Mathematics

The m-spotty byte error control codes provide a good source for detecting and correcting errors in semiconductor memory systems using high density RAM chips with wide I/O data (e.g. 8, 16, or 32 bits). m-spotty byte error control codes are very suitable for burst correction. Here, we introduce the m-spotty weights and m-spotty weight enumerator of linear codes over the ring F_2+uF_2 and prove a MacWilliams type identity.


Multiplication Modules With Krull Dimension, Mahmood Behboodi, Maryam Molakarimi Jan 2012

Multiplication Modules With Krull Dimension, Mahmood Behboodi, Maryam Molakarimi

Turkish Journal of Mathematics

In ring theory, it is shown that a commutative ring R with Krull dimension has classical Krull dimension and satisfies k.dim(R)=cl.k.dim(R). Moreover, R has only a finite number of distinct minimal prime ideals and some finite product of the minimal primes is zero (see Gordon and Robson [9, Theorem 8.12, Corollary 8.14, and Proposition 7.3]). In this paper, we give a generalization of these facts for multiplication modules over commutative rings. Actually, among other results, we prove that if M is a multiplication R-module with Krull dimension, then: (i) M is finitely generated, (ii) R has finitely many minimal prime …


Uc Modules With Respect To A Torsion Theory, Seçi̇l Çeken, Mustafa Alkan Jan 2012

Uc Modules With Respect To A Torsion Theory, Seçi̇l Çeken, Mustafa Alkan

Turkish Journal of Mathematics

In this paper, we give some characterizations of modules M over a ring R such that every submodule has a unique closure relative to a hereditary torsion theory on Mod-R by using the concept of \tau-closed submodule which was studied in [2]. We compare UC and \tau-UC modules and examine the relationships between them. We also give some examples of \tau-UC and UC modules and submodules which have a unique \tau-closure and unique closure.


Oscillation Of Third-Order Nonlinear Delay Difference Equations, Mustafa Fahri̇ Aktaş, Aydin Ti̇ryaki̇, Ağacik Zafer Jan 2012

Oscillation Of Third-Order Nonlinear Delay Difference Equations, Mustafa Fahri̇ Aktaş, Aydin Ti̇ryaki̇, Ağacik Zafer

Turkish Journal of Mathematics

Third-order nonlinear difference equations of the form \Delta (c_n\Delta (d_n\Delta x_n))+p_n\Delta x_{n+1}+q_nf(x_{n-\sigma})=0, n\geq n_{0} are considered. Here, {c_n}, {d_n}, {p_n}, and {q_n} are sequences of positive real numbers for n_0 \in N, f is a continuous function such that f(u) /u\geq K > 0 for u \neq 0. By means of a Riccati transformation technique we obtain some new oscillation criteria. Examples are given to illustrate the importance of the results.


Simultaneous Proximinality Of Vector Valued Function Spaces, Mona Khandaqji, Fadi Awawdeh, Jamila Jawdat Jan 2012

Simultaneous Proximinality Of Vector Valued Function Spaces, Mona Khandaqji, Fadi Awawdeh, Jamila Jawdat

Turkish Journal of Mathematics

A characterization of best simultaneous approximation of Köthe spaces of vector-valued functions is given. This characterization is a generalization of some analogous theorems for Orlicz Bochner spaces.


Weight And Nonlinearity Of Boolean Functions, Lavinia Corina Ciungu Jan 2012

Weight And Nonlinearity Of Boolean Functions, Lavinia Corina Ciungu

Turkish Journal of Mathematics

In this paper we analyze the weight and the nonlinearity of various types of Boolean functions. We give some general results related to rotation symmetric Boolean functions, and in particular, we prove partially a conjecture stated by Cusick and Stanica in [3].


Product Of Graded Submodules, Ameer Jaber Jan 2012

Product Of Graded Submodules, Ameer Jaber

Turkish Journal of Mathematics

Let \Delta be an abelian group. By considering the notion multiplication of \Delta-graded modules (see [7]) over a commutative \Delta-graded ring with unity, we introduce the notion of product of two \Delta-graded submodules which we use to characterize the \Delta-graded prime submodules of a multiplication \Delta-graded module. Finally we proved a graded version of Nakayama lemma for multiplication \Delta-graded modules.


On The Order Of Weighted Approximation By Positive Linear Operators, Tüli̇n Coşkun Jan 2012

On The Order Of Weighted Approximation By Positive Linear Operators, Tüli̇n Coşkun

Turkish Journal of Mathematics

An estimation of approximation of continuous functions by positive linear operators in weighted norm using the weighted modulus of continuity is established. Application of the main result to the known Gadjiyev-Ibragimov operators is given.


Banach Limit And Some New Spaces Of Double Sequences, Mohammad Mursaleen, Syed Abdul Mohiuddine Jan 2012

Banach Limit And Some New Spaces Of Double Sequences, Mohammad Mursaleen, Syed Abdul Mohiuddine

Turkish Journal of Mathematics

In this paper, we define and study the Banach limit for double sequences and introduce some new spaces related to the concept of almost and strong almost convergence for double sequences. We characterize these spaces through some sublinear functionals and we also establish some inclusion relations.


C^*-Convexity And C^*-Faces In *-Rings, Ali Ebrahimi Meymand, Gholam Hossein Esslamzadeh Jan 2012

C^*-Convexity And C^*-Faces In *-Rings, Ali Ebrahimi Meymand, Gholam Hossein Esslamzadeh

Turkish Journal of Mathematics

Existence of rich algebraic, geometric and topological structures on self-adjoint operator algebras raises the general question that, for a particular theorem which of these structures have made the result work. The present paper is an effort toward the answer of this question, by investigating the role of algebraic structure in the subject of C^*-convexity. In this paper, we extend the notions of C^*-convexity, C^*-extreme point and C^*-face to *-rings and we study some of their properties. We introduce the notion of C^*-convex map on C^*-convex subsets of a *-ring. Moreover we identify optimal points of some unital *-homomorphisms on some …


On Cise-Normal Subgroups Of Finite Groups, Yong Xu, Tao Zhao, Xianhua Li Jan 2012

On Cise-Normal Subgroups Of Finite Groups, Yong Xu, Tao Zhao, Xianhua Li

Turkish Journal of Mathematics

A generalized normality CISE of subgroups of a finite group is introduced. Let F be a saturated formation containing the class of all supersolvable groups. We give a characterization of F by using CISE-normality of subgroups.


On Normality Of Meromorphic Functions With Multiple Zeros And Sharing Values, Youming Wang Jan 2012

On Normality Of Meromorphic Functions With Multiple Zeros And Sharing Values, Youming Wang

Turkish Journal of Mathematics

In this paper we study the problem of normal families of meromorphic functions concerning shared values. Let F be a family of meromorphic functions in the plane domain D \subseteq C and n be a positive integer. Let a, b be two finite complex constants such that a \neq 0. If n \geq 3 and f + a(f')^n and g + a(g')^n share b in D for every pair of functions f, g \in F, then F is normal in D. And some examples are provided to show the result is sharp.


Invariant Subspaces Of Weakly Compact-Friendly Operators, Mert Çağlar, Remzi̇ Tunç Misirlioğlu Jan 2012

Invariant Subspaces Of Weakly Compact-Friendly Operators, Mert Çağlar, Remzi̇ Tunç Misirlioğlu

Turkish Journal of Mathematics

We prove that if a non-zero weakly compact-friendly operator B on a Banach lattice with topologically full center is locally quasi-nilpotent, then the super right-commutant [B\rangle of B has a non-trivial closed invariant ideal. An example of a weakly compact-friendly operator which is not compact-friendly is also provided.


Value Distribution Of Meromorphic Functions And Their Differences, Ranran Zhang, Zongxuan Chen Jan 2012

Value Distribution Of Meromorphic Functions And Their Differences, Ranran Zhang, Zongxuan Chen

Turkish Journal of Mathematics

Let f(z) be a transcendental meromorphic function. Results are proved concerning the value distribution of the n'th forward difference \Delta^nf(z), in terms of Borel exceptional values of f(z). The results may be partly viewed as discrete analogues of a classical theorem of Hayman dealing with the possible relationships between Picard exceptional values of f(z) and its derivatives.


Generalized Berwald Metrics, Esmaeil Peyghan, Akbar Tayebi Jan 2012

Generalized Berwald Metrics, Esmaeil Peyghan, Akbar Tayebi

Turkish Journal of Mathematics

In this paper, we consider a class of Finsler metrics called generalized Berwald metrics which contains the class of Berwald metrics as a special case. We prove that every generalized Berwald metrics with non-zero scalar flag curvature or isotropic Berwald curvature is a Randers metric. Then we prove that on generalized Berwald metrics, the notions of generalized Landsberg and Landsberg curvatures are equivalent.


Bruhat-Chevalley Order On The Rook Monoid, Mahi̇r Bi̇len Can, Lex E. Renner Jan 2012

Bruhat-Chevalley Order On The Rook Monoid, Mahi̇r Bi̇len Can, Lex E. Renner

Turkish Journal of Mathematics

The rook monoid R_n is the finite monoid whose elements are the 0-1 matrices with at most one nonzero entry in each row and column. The group of invertible elements of R_n is isomorphic to the symmetric group S_n. The natural extension to R_n of the Bruhat-Chevalley ordering on the symmetric group is defined in [1]. In this paper, we find an efficient, combinatorial description of the Bruhat-Chevalley ordering on R_n. We also give a useful, combinatorial formula for the length function on R_n.


Results Of Generalized Local Cohomology Modules Of A-Minimax Modules, Hero Saremi Jan 2012

Results Of Generalized Local Cohomology Modules Of A-Minimax Modules, Hero Saremi

Turkish Journal of Mathematics

Let R be a commutative Noetherian ring, M a finitely generated R-module, and N a minimax R-module. It is shown that if a is an ideal of R, such that cd(a)=1, where cd is the cohomological dimension of a in R, then H_a^j(M, N) and Ext_R^i(M,H_a^j(N)) are a-cominimax for all i,j. Furthermore, if t is a non-negative integer such that H_a^j(M, N) is a-minimax for all j