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Full-Text Articles in Physical Sciences and Mathematics

On The Existence Of Nonzero Injective Covers And Projective Envelopes Of Modules, Xiaoxiang Zhang, Xianmei Song Jan 2013

On The Existence Of Nonzero Injective Covers And Projective Envelopes Of Modules, Xiaoxiang Zhang, Xianmei Song

Turkish Journal of Mathematics

In general, the injective cover (projective envelope) of a simple module can be zero. A ring R is called a weakly left V-ring (strongly left Kasch ring) if every simple left R-module has a nonzero injective cover (projective envelope). It is proven that every nonzero left R-module has a nonzero injective cover if and only if R is a left Artinian weakly left V-ring. Dually, every nonzero left R-module has a nonzero projective envelope if and only if R is a left perfect right coherent strongly left Kasch ring. Some related rings and examples are considered.


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.


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.


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.


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 …


On The Automorphisms Of Direct Product Of Monogenic Semigroups And Monoids, Karim Ahmadidelir, Hossein Doostie Jan 2012

On The Automorphisms Of Direct Product Of Monogenic Semigroups And Monoids, Karim Ahmadidelir, Hossein Doostie

Turkish Journal of Mathematics

This paper investigates the automorphism group of monogenic [4] semigroups (or monoids) to find its relationship with the automorphism group of cyclic groups. Then, by considering a presentation related to the direct product of monogenic semigroups, verify the relationship between the automorphism group of These and the automorphism group of the group presented by the same presentation. This study gives us some [4]explicit formulas for computing the order of automorphism groups of these algebraic structures.


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.


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 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.


Note On Hilbert-Type Inequalities, Predrag Vukovic Jan 2012

Note On Hilbert-Type Inequalities, Predrag Vukovic

Turkish Journal of Mathematics

The main objective of this paper is to prove Hilbert-type and Hardy-Hilbert-type inequalities with a general homogeneous kernel, thus generalizing a result obtained in [Namita Das and Srinibas Sahoo, A generalization of multiple Hardy-Hilbert's integral inequality, Journal of Mathematical Inequalities, 3(1), (2009), 139--154].


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.


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.


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].


Pointwise Slant Submanifolds In Almost Hermitian Manifolds, Bang-Yen Chen, Oscar J. Garay Jan 2012

Pointwise Slant Submanifolds In Almost Hermitian Manifolds, Bang-Yen Chen, Oscar J. Garay

Turkish Journal of Mathematics

An interesting class of submanifolds of almost Hermitian manifolds (\tilde M,\tilde g,J) is the class of slant submanifolds. Slant submanifolds were introduced by the first author in [6] as submanifolds M of (\tilde M,\tilde g,J) such that, for any nonzero vector X \in T_pM, p \in M, the angle \theta(X) between JX and the tangent space T_pM is independent of the choice of p\in M and X \in T_pM. The first results on slant submanifolds were summarized in the book [7]. Since then slant submanifolds have been studied by many geometers. Many nice results on slant submanifolds have been obtained …


Extended Cross Product In A 3-Dimensional Almost Contact Metric Manifold With Applications To Curve Theory, Çeti̇n Camci Jan 2012

Extended Cross Product In A 3-Dimensional Almost Contact Metric Manifold With Applications To Curve Theory, Çeti̇n Camci

Turkish Journal of Mathematics

In this work, we define a new cross product in 3-dimensional almost contact metric manifold and we study the theory of curves using this new cross product in this manifold. Besides, in the works of Baikousis, Blair [1] and Cho et al. [4], we observe that some theorems are incomplete and excessively generalized are thus their alternative proofs presented.


Warped Product Submanifolds Of A Kenmotsu Manifold, Siraj Uddin, Viqar Azam Khan, Khalid Ali Khan Jan 2012

Warped Product Submanifolds Of A Kenmotsu Manifold, Siraj Uddin, Viqar Azam Khan, Khalid Ali Khan

Turkish Journal of Mathematics

In the present paper, we study warped product semi-slant submanifolds of a Kenmotsu manifold. We obtain some results on the existence of such type warped product submanifolds of a Kenmotsu manifold with an example.


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.


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.


The Character Variety Of A Class Of Rational Links, Khaled Qazaqzeh Jan 2012

The Character Variety Of A Class Of Rational Links, Khaled Qazaqzeh

Turkish Journal of Mathematics

Let G_n be the fundamental group of the exterior of the rational link C(2n) in Conway's normal form, see [7]. A presentation for G_n is given by \langle a, b (ab)^n = (ba)^n\rangle [3, Thm. 2.2]. We study the character variety in SL(2, C) of the group G_n. In particular, we give the defining polynomial of the character variety of G_n. As an application, we show a well-known result that G_n and G_m are isomorphic only when n = m. Also as a consequence of the main theorem of this paper, we give a basis of the Kauffman bracket skein …


On F_S-Supplemented Primary Subgroups Of Finite Groups, Lujin Zhu, Long Miao Jan 2012

On F_S-Supplemented Primary Subgroups Of Finite Groups, Lujin Zhu, Long Miao

Turkish Journal of Mathematics

Let G be a finite group and F a formation of finite groups. A subgroup H of G is called F_s-supplemented in G if there exists a subnormal subgroup T of G such that G = HT and (H \cap T)H_G/H_G is contained in the F-hypercenter Z^F_{\infty}(G/H_G) of G/H_G. In this paper, we study the structure of finite groups by using F_s-supplemented subgroups.


On Cosets In Coxeter Groups, Sarah B. Hart, Peter J. Rowley Jan 2012

On Cosets In Coxeter Groups, Sarah B. Hart, Peter J. Rowley

Turkish Journal of Mathematics

In this paper the notion of Coxeter length for a subset of a Coxeter group, as introduced in [9], is investigated for various subsets of a Coxeter group. Mostly cosets of various subgroups are examined as well as the associated idea of X-posets, which is a vast generalization of the Bruhat order.


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 …


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.


On Injective And Subdirectly Irreducible S-Acts Over Left Zero Semigroups, Gholamreza Moghaddasi Jan 2012

On Injective And Subdirectly Irreducible S-Acts Over Left Zero Semigroups, Gholamreza Moghaddasi

Turkish Journal of Mathematics

The aim of this paper is to characterize subdirectly irreducible S-acts over left zero semigroups. Also we compute the number of such acts and specify cogenerators acts over left zero semigroups. To do these we first take another look at the description of injective hulls of the separated S-acts over left zero semigroups.


L^P Regularity Of Some Weighted Bergman Projections On The Unit Disc, Yunus Ergi̇n Zeytuncu Jan 2012

L^P Regularity Of Some Weighted Bergman Projections On The Unit Disc, Yunus Ergi̇n Zeytuncu

Turkish Journal of Mathematics

We show that weighted Bergman projections, corresponding to weights of the form M(z)(1- z ^2)^\alpha, where \alpha > -1 and M(z) is a radially symmetric, strictly positive and at least C^2 function on \overline{D}, are L^p regular.


Superinjective Simplicial Maps Of The Complexes Of Curves On Nonorientable Surfaces, Elmas Irmak Jan 2012

Superinjective Simplicial Maps Of The Complexes Of Curves On Nonorientable Surfaces, Elmas Irmak

Turkish Journal of Mathematics

We prove that each superinjective simplicial map of the complex of curves of a compact, connected, nonorientable surface is induced by a homeomorphism of the surface, if (g, n) \in {(1, 0), (1, 1), (2, 0), (2, 1), (3, 0)} or g + n \geq 5, where g is the genus of the surface and n is the number of the boundary components.


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.