Volume 66 , issue 4 ( 2014 ) back
 $\beta$-greedoids 343$-$350 Talal Al-Hawary

Abstract

In this paper, we introduce the notion of $\beta$-greedoids and discuss four basic constructions of $\beta$-greedoids namely, deletion, contraction, direct sum and ordered sum. We show that the operations of deletion and contraction commute and the direct sum and ordered sum of $\beta$-greedoids $G_{1}$ and $G_{2}$ are interval $\beta$-greedoids if and only if $G_{1}$ and $G_{2}$ are both interval $\beta$-greedoids. We also give a necessary and sufficient condition for the direct sum and ordered sum of balanced $\beta$-greedoids to be balanced.

Keywords: $\beta$-greedoid; basis; feasible; flat; density; direct sum; ordered sum.

MSC: 52C99

 Fixed point for fuzzy contraction mappings satisfying an implicit relation 351$-$356 Ismat Beg and M. A. Ahmed

Abstract

We prove a common fixed point theorem for generalized fuzzy contraction mappings satisfying an implicit relation.

Keywords: Fuzzy sets; fuzzy map; fuzzy contractive mappings; common fixed points.

MSC: 47H10, 54H25

 A remark on the property $\mathcal P$ and periodic points of order $ınfty$ 357$-$363 Parin Chaipunya, Yeol Je Cho and Poom Kumam

Abstract

In this paper, we considered the relationship between periodic points, fixed points, and the property $\mathcal P$. We also presented an extended version of periodic points together with their behaviors in topological spaces and cone metric spaces.

Keywords: Metric space; property $\mathcal P$; periodic point.

MSC: 47H09, 47H10

 $n$-normal and $n$-quasinormal composition and weighted composition operators on $L^{2}(\mu)$ 364$-$370 Anuradha Gupta and Neha Bhatia

Abstract

An operator $T$ is called $n$-normal operator if $T^nT^* = T^*T^n$ and $n$-quasinormal operator if $T^nT^*T = T^*TT^n$. In this paper, the conditions under which composition operators and weighted composition operators become $n$-normal operators and $n$-quasinormal operators have been obtained in terms of Radon-Nikodym derivative $h_n$.

Keywords: normal operator; quasinormal operator; $n$-normal operator; $n$-quasinormal operator; composition operator; weighted composition operator; conditional expectation operator; hyponormal operator; compact operator.

MSC: 47B20, 47B33, 47B38

 Lightlike submanifolds of indefinite para-Sasakian manifolds 371$-$386 S. S. Shukla and Akhilesh Yadav

Abstract

In this paper, we study invariant, slant and screen slant lightlike submanifolds of indefinite para-Sasakian manifolds. We obtain necessary and sufficient conditions for existence of slant and screen slant lightlike submanifolds of indefinite para-Sasakian manifolds and also provide non-trivial examples of such submanifolds. We obtain integrability conditions of distributions $D$ and $RadTM$ on screen slant lightlike submanifolds of indefinite para-Sasakian manifold. Further we obtain sufficient condition for induced connection on screen slant lightlike submanifolds of indefinite para-Sasakian manifold to be metric connection.

Keywords: Semi-Riemannian manifold; degenerate metric; radical distribution; screen distribution; screen transversal vector bundle; Gauss and Weingarten formulae; totally geodesic and totally umbilical lightlike submanifold.

MSC: 53C15, 53C40, 53C50

 Univariate fractional Polya type integral inequalities 387$-$396 George A. Anastassiou

Abstract

Here we establish a series of various fractional Polya type integral inequalities with the help of generalized right and left fractional derivatives. We give an application to complex valued functions defined on the unit circle.

Keywords: Polya integral inequality; fractional derivative.

MSC: 26A33, 26D10, 26D15

 Common fixed points of two multivalued nonexpansive maps by a one-step implicit algorithm in hyperbolic spaces 397$-$409 S. H. Khan, H. Fukhar-ud-din and A. Kalsoom

Abstract

In this paper, we construct an implicit algorithm for two multivalued nonexpansive maps in a hyperbolic space and use it to approximate common fixed points of these maps through $\triangle$-convergence and strong convergence.

Keywords: Common fixed point; hyperbolic space; implicit algorithm; multivalued nonexpansive map; strong convergence; $\triangle$-convergence.

MSC: 47A06, 47H09, 47H10, 49M05

 Results concerning symmetric generalized biderivations of prime and semiprime rings 410$-$417 Asma Ali, V. De Filippis and Faiza Shujat

Abstract

The purpose of this paper is to prove some results concerning symmetric biderivations and symmetric generalized biderivations on prime and semiprime rings which partially extend some results contained in Vukman, J., Symmetric biderivations on prime and semiprime rings, Aequationes Math. 38 (1989), 245--254 and Vukman, J., Two results concerning symmetric biderivations on prime rings, Aequationes Math. 40 (1990), 181--189.

Keywords: Semiprime ring; generalized derivation; symmetric biderivation.

MSC: 16R50, 16W25, 16N60

 Elliptic transmission problem in disjoint domains 418$-$429 Zorica D. Milovanović

Abstract

In this paper, we investigate an elliptic transmission problem in disjoint domains. A priori estimate for its weak solution in appropriate Sobolev-like space is proved. A finite difference scheme approximating this problem is proposed and analyzed. An estimate of the convergence rate, compatible with the smoothness of the input data (up to a slowly increasing logarithmic factor of the mesh size), is obtained.

Keywords: Elliptic transmission problem; disjoint domains; Sobolev-like space.

MSC: 65N12, 65N15

 Compact families and continuity of the inverse 430$-$436 Brian L. Davis

Abstract

We generalize a topological game introduced by Kenderov, Kortezov and Moors and use it to establish conditions under which a paratopological group is a topological group.

Keywords: Cover; filter; compact filter; topological group; paratopological group; topological game.

MSC: 54D30