فهرست مطالب
Bulletin of Iranian Mathematical Society
Volume:41 Issue: 6, 2015
- تاریخ انتشار: 1394/10/10
- تعداد عناوین: 20
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Pages 1315-1326We consider the uniqueness problem of algebroid functions on an angular domain. Several theorems are established to extend the uniqueness theory of meromorphic functions to algebroid functions.Keywords: Algebroid functionsý, ýNevanlinnaý ýtheoryý, angular domainý, ýUniquenessý
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Pages 1327-1337The objective of this paper is to obtain an upper bound to the second Hankel determinant |a 2 a 4 −a 2 3 | |a2a4−a32| for the function f f, belonging to the class of Gamma-starlike functions, using Toeplitz determinants. The result presented here include two known results as their special cases.Keywords: Analytic functioný, ýgamma, starlike functioný, ýsecond Hankel functionalý, ýpositive real functioný, ýToeplitz determinantsý
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Pages 1339-1344A total dominating set of a graph G G is a set D D of vertices of G G such that every vertex of G G has a neighbor in D D . The total domination number of a graph G G , denoted by γ t (G) γt(G) , is~the minimum cardinality of a total dominating set of G G . Chellali and Haynes [Total and paired-domination numbers of a tree, AKCE International ournal of Graphs and Combinatorics 1 (2004), 69--75] established the following upper bound on the total domination number of a tree in terms of the order and the number of support vertices, γ t (T)≤(n+s)/2 γt(T)≤(n+s)/2 . We characterize all trees attaining this upper bound.Keywords: ýDýominationý, ýtotal dominationý, ýtree
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Pages 1345-1353Two types of properties for linear connections (natural and almost paracontact metric) are discussed in almost paracontact metric geometry with respect to four linear connections: Levi-Civita, canonical (Zamkovoy), Golab and generalized dual. Their relationship is also analyzed with a special view towards their curvature. The particular case of an almost paracosymplectic manifold gives a major simplification in computations since the paracontact form is closed.Keywords: Almost paracontact metric manifold?, ?natural connection?, ?canonical connection?, ?Golab connection?, ?generalized dual connections?
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Pages 1355-1363The class of ads modules with the SIP (briefly, SA SA -modules) is studied. Various conditions for a module to be SA SA -module are given. It is proved that for a quasi-continuous module M M , M M is a UC-module if and only if M M is an SA SA -module. Also, it is proved that the direct sum of two SA SA -modules as R R -modules is an SA SA -module when R R is the sum of the annihilators of these modules.Keywords: Ads, modulesý, ýsummand intersection propertyý, ýextending modulesý
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Pages 1365-1374A ring R R is strongly clean provided that every element in R R is the sum of an idempotent and a unit that commutate. Let T n (R,σ) Tn(R,σ) be the skew triangular matrix ring over a local ring R R where σ σ is an endomorphism of R R. We show that T 2 (R,σ) T2(R,σ) is strongly clean if and only if for any a∈1+J(R),b∈J(R) a∈1+J(R),b∈J(R), l a −r σ(b) :R→R la−rσ(b):R→R is surjective. Further, T 3 (R,σ) T3(R,σ) is strongly clean if l a −r σ(b) ,l a −r σ 2 (b) la−rσ(b),la−rσ2(b) and l b −r σ(a) lb−rσ(a) are surjective for any a∈U(R),b∈J(R) a∈U(R),b∈J(R) . The necessary condition for T 3 (R,σ) T3(R,σ) to be strongly clean is also obtained. Keywords: Strongly clean ringsý, ýskew triangular matrix ringsý, ýlocal ringsý
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Pages 1375-1386In this paper, we introduce α α -ψ ψ -contractive mapping in partially ordered sets and construct fixed point theorems to solve a first-order ordinary differential equation by existence of its lower solution.Keywords: Fixed point?, ?? ?, ? ?, contractive mappings?, ?partially ordered sets?, ?lower, upper solutions?
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Pages 1387-1399Using the fixed point theorem in a cone, the existence and multiplicity of radial convex solutions of singular system of Monge-Amp\`{e}re equations are established.Keywords: Singular Monge, Amp\'{e}re system, radial convex solution, ý ýFixed point theorem
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Pages 1401-1412Making use of a linear operator, which is defined here by means of the Hadamard product (or convolution), we define a subclass Tp(a,c,γ,λ;h) of meromorphically multivalent functions. The main object of this paper is to investigate some important properties for the class. We also derive many results for the Hadamard roducts of functions belonging to the class.Keywords: Meromorphically multivalent functionsý, ýconvexý ýunivalentý ýfunctionsý, ýHadamard productý, ýsubordinationý
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Pages 1413-1422In this paper, we introduce and study a class of generalized vector quasi-equilibrium problem, which includes many vector equilibrium problems, equilibrium problems, vector variational inequalities and variational inequalities as special cases. Using one person game theorems, the concept of escaping sequences and without convexity assumptions, we prove some existence results for generalized vector quasi-equilibrium problem.Keywords: Vector quasi, equilibrium problemý, ýescaping sequenceý, ýexistenceý, ýcontinuity
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Pages 1423-1431For a finite group G G , let Cent(G) Cent(G) denote the set of centralizers of single elements of G G . In this note we prove that if |G|≤32 |Cent(G)| |G|≤32|Cent(G)| and G G is 2-nilpotent, then G≅S 3 ,D 10 G≅S3,D10 or S 3 ×S 3 S3×S3 . This result gives a partial and positive answer to a conjecture raised by A. R. Ashrafi [On finite groups with a given number of centralizers, Algebra Colloq. 7 (2000), no. 2, 139- 146].Keywords: finite groups, centralizer, involution
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Pages 1433-1444In this paper, we investigate the existence of solution for a k-dimensional system of three points nabla fractional finite difference equations. Also, we present an example to illustrate our result.Keywords: Fixed point, Fractional finite difference equation, k, dimensional system
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Pages 1445-1452In Proposition 2.6 in (G. Gruenhage, A. Lutzer, Baire and Volterra spaces, \textit{Proc. Amer. Math. Soc.} {128} (2000), no. 10, 3115--3124) a condition that every point of D D is G δ Gδ in X X was overlooked. So we proved some conditions by which a Baire space is equivalent to a Volterra space. In this note we show that if X X is a monotonically normal T 1 T1 -space with countable pseudocharacter and X X has a σ σ -discrete dense subspace D D , then X X is a Baire space if and only if X X is Volterra. We show that if X X is a metacompact normal sequential T 1 T1 -space and X X has a σ σ -closed discrete dense subset, then X X is a Baire space if and only if X X is Volterra. If X X is a generalized ordered (GO) space and has a σ σ -closed discrete dense subset, then X X is a Baire space if and only if X X is Volterra. And also some known results are generalized.Keywords: Volterra space, Baire space, monotonically normal, metacompact
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Pages 1453-1464In this paper a nonlinear backward parabolic problem in one dimensional space is considered. Using a suitable iterative algorithm, the problem is converted to a linear backward parabolic problem. For the corresponding problem, the backward finite differences method with suitable grid size is applied. It is shown that if the coefficients satisfy some special conditions, this algorithm not only is convergent, but also is conditionally stable. Moreover, it is proved that the estimated values converge to the exact solution of the problem. Al these approaches examined in some numerical examples. corresponding theorems for the convergency and stability of the solution are studied.Keywords: Nonlinear backward parabolic problemý, ýlinearý ýbackward parabolic problemý, ýiterative algorithmý, ýstabilityý, ýconvergency
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Pages 1465-1475Let R R be a ring with involution ∗ ∗ . An additive mapping T:R→R T:R→R is called a left(respectively right) centralizer if T(xy)=T(x)y T(xy)=T(x)y (respectively T(xy)=xT(y) T(xy)=xT(y)) for all x,y∈R x,y∈R . The purpose of this paper is to examine the commutativity of prime rings with involution satisfying certain identities involving left centralizers.Keywords: Prime ring, normal ring, involution, Left centralizer, centralizer
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Pages 1477-1492By considering a degenerate p(x)− p(x)− Laplacian equation, a generalized compact embedding in weighted variable exponent Sobolev space is presented. Multiplicity of positive solutions are discussed by applying fibering map approach for the corresponding Nehari manifold.Keywords: Nehari Manifoldý, ýfibering mapý, ýweak solutioný, ývariable exponent Lebesgue spaceý, ývariable exponent Sobolev space
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Pages 1493-1495For a finite group G G let nu(G) nu(G) denote the number of conjugacy classes of non-normal subgroups of G G. We give a short proof of a theorem of Brandl, which classifies finite groups with nu(G = nu(G)=1.Keywords: ?Dedekind groups, conjugacy classes of non, normal subgroups, classification of finite groups
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Pages 1497-1509For Fracutemathbftexte acutemathbftexte chet algebras (A,(p n)) (A,(pn)) and (B,(q n)) (B,(qn)), a linear map T:ArightarrowB T:ArightarrowB is textit{almost multiplicative} with respect to (p n) (pn) and (q n) (qn), if there exists varepsilongeq0 varepsilongeq0 such that q n (Tab−TaTb)leqvarepsilonp n (a)p n (b), qn(Tab−TaTb)leqvarepsilonpn(a)pn(b), for all ninmathbbN ninmathbbN, a,binA a,binA, and it is called textit{weakly almost multiplicative} with respect to (p n) (pn) and (q n) (qn), if there exists varepsilongeq0 varepsilongeq0 such that for every kinmathbbN kinmathbbN, there exists n(k)inmathbbN n(k)inmathbbN, satisfying the inequality q k (Tab−TaTb)leqvarepsilonp n(k) (a)p n(k) (b), qk(Tab−TaTb)leqvarepsilonpn(k)(a)pn(k)(b), for all a,binA a,binA. We investigate the automatic continuity of (weakly) almost multiplicative maps between certain classes of Fracutemathbftexte acutemathbftexte chet algebras, such as Banach algebras and Fracutemathbftexte acutemathbftexte chet Q Q -algebras. We also obtain some results on the automatic continuity of dense range (weakly) almost multiplicative maps between Fracutemathbftexte acutemathbftexte chet algebras.Keywords: ýAutomatic continuityý_ýFre ´ e´ chetý ýalgebrasý_ýQ Q_algebrasý_almost multiplicative mapsý_weakly almostý ýmultiplicative mapsý_dense range almostý ýmultiplicative maps
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Pages 1511-1517In this paper, we consider the boundedness of the Libera operator on Dirichlet spaces in terms of the Schur test. Moreover, we get its point spectrum and norm.Keywords: Libera operator, Dirichlet spaces, point spectrum, norm
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Pages 1519-1535This paper deals with scrutinizing the convergence properties of iterative methods to solve linear system of equations. Recently, several types of the preconditioners have been applied for ameliorating the rate of convergence of the Accelerated Overrelaxation (AOR) method. In this paper, we study the applicability of a general class of the preconditioned iterative methods under certain conditions. More precisely, it is demonstrated that the preconditioned Mixed-Type Splitting (MTS) iterative methods can surpass the preconditioned AOR iterative methods for an entirely general class of preconditioners handled by Wang and Song [J. Comput. Appl. Math. 226 (2009), no. 1, 114--124]. Finally some numerical results are elaborated which confirm the validity of the established results.Keywords: ýLinear system, iterative method, mixed, Type splitting, preconditioner, convergence rate