eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
1
7
479
A lower estimate of harmonic functions
Guoshuang Pan
gsp1979@163.com
1
Lei Qiao
qiaocqu@163.com
2
Guantie Deng
denggt@bnu.edu.cn
3
Beijing National Day School
Department of Mathematics and Information Science, Henan University of Economics and Law, Zhengzhou, People's Republic of China
School of Mathematical
Science, Beijing Normal University, Beijing, People's Republic of China.
We shall give a lower estimate of harmonic functions of order greater than one in a half space, which generalize the result obtained by B. Ya. Levin in a half plane.
http://bims.iranjournals.ir/article_479_2cdf12321f02f3726af6042859a49ca3.pdf
Lower estimate
Harmonic function
Half space
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
9
28
480
Investigation on the Hermitian matrix expression subject to some consistent equations
Xiang Zhang
zxjnsc@163.com
1
Department of Mathematics, Zunyi Normal College Shanghai Road, Zunyi
563000, P.R. China
In this paper, we study the extremal ranks and inertias of the Hermitian matrix expression $$ f(X,Y)=C_{4}-B_{4}Y-(B_{4}Y)^{*}-A_{4}XA_{4}^{*},$$ where $C_{4}$ is Hermitian, $*$ denotes the conjugate transpose, $X$ and $Y$ satisfy the following consistent system of matrix equations $A_{3}Y=C_{3}, A_{1}X=C_{1},XB_{1}=D_{1},A_{2}XA_{2}^{*}=C_{2},X=X^{*}.$ As consequences, we get the necessary and sufficient conditions for the above expression $f(X,Y)$ to be (semi) positive, (semi) negative. The relations between the Hermitian part of the solution to the matrix equation $A_{3}Y=C_{3}$ and the Hermitian solution to the system of matrix equations $A_{1}X=C_{1},XB_{1}=D_{1},A_{2}XA_{2}^{*}=C_{2}$ are also characterized. Moreover, we give the necessary and sufficient conditions for the solvability to the following system of matrix equations $A_{3}Y=C_{3},A_{1}X=C_{1},XB_{1}=D_{1}, A_{2}XA_{2}^{*}=C_{2},X=X^{*}, B_{4}Y+(B_{4}Y)^{*}+A_{4}XA_{4}^{*}=C_{4} $ and provide an expression of the general solution to this system when it is solvable.
http://bims.iranjournals.ir/article_480_368a4a67459524d7aa8a44355b07f8d1.pdf
Linear matrix equation
Moore-Penrose inverse
Rank
Inertia
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
29
40
481
Coupled fixed point results for weakly related mappings in partially ordered metric spaces
Naval Singh
drsinghnaval@gmail.com
1
Reena Jain
reenakhatod@gmail.com
2
govt. benazir college, bhopal
Technocrats Institute of technology
In the present paper, we show the existence of a coupled fixed point for a non-decreasing mapping in partially ordered complete metric space using a partial order induced by an appropriate function $phi$. We also define the concept of weakly related mappings on an ordered space. Moreover common coupled fixed points for two and three weakly related mappings are also proved in the same space.
http://bims.iranjournals.ir/article_481_4e6a03a572aeff155f37a395d5757e77.pdf
Coupled fixed point
common coupled fixed point
partially ordered space
weakly related mappings
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
41
53
482
A matrix LSQR algorithm for solving constrained linear operator equations
Masoud Hajarian
mhajarian@aut.ac.ir
1
Department of Mathematics
Faculty of Mathematical Sciences
Shahid Beheshti University, G.C.,
Evin, Tehran 19839
Iran
In this work, an iterative method based on a matrix form of LSQR algorithm is constructed for solving the linear operator equation $mathcal{A}(X)=B$ and the minimum Frobenius norm residual problem $||mathcal{A}(X)-B||_F$ where $Xin mathcal{S}:={Xin textsf{R}^{ntimes n}~|~X=mathcal{G}(X)}$, $mathcal{F}$ is the linear operator from $textsf{R}^{ntimes n}$ onto $textsf{R}^{rtimes s}$, $mathcal{G}$ is a linear self-conjugate involution operator and $Bin textsf{R}^{rtimes s}$. Numerical examples are given to verify the efficiency of the constructed method.
http://bims.iranjournals.ir/article_482_84ccde0152b76da6ba408ddf2be03cef.pdf
Iterative method
Bidiagonalization procedure
Linear operator equation
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
55
81
483
Maximal prehomogeneous subspaces on classical groups
Xiaoxiang Yu
carston123@126.com
1
Dengyin Wang
wdengyin@126.com
2
Xuzhou Normal University,
P.R.China
China University of Mining and technology
Suppose $G$ is a split connected reductive orthogonal or symplectic group over an infinite field $F,$ $P=MN$ is a maximal parabolic subgroup of $G,$ $frak{n}$ is the Lie algebra of the unipotent radical $N.$ Under the adjoint action of its stabilizer in $M,$ every maximal prehomogeneous subspaces of $frak{n}$ is determined.
http://bims.iranjournals.ir/article_483_e3bd93459034ea5c23b49e16867e543d.pdf
prehomogeneous space
adjoint action
orthogonal
symplectic
orbit
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
83
100
484
Sequential second derivative general linear methods for stiff systems
Ali Ezzeddine
aliezz@tabrizu.ac.ir
1
Gholamreza Hojjati
ghojjati@yahoo.com
2
Ali Abdi
a_abdi@tabrizu.ac.ir
3
University of Tabriz
University of Tabriz
University of Tabriz
Second derivative general linear methods (SGLMs) as an extension of general linear methods (GLMs) have been introduced to improve the stability and accuracy properties of GLMs. The coefficients of SGLMs are given by six matrices, instead of four matrices for GLMs, which are obtained by solving nonlinear systems of order and usually Runge--Kutta stability conditions. In this paper, we introduce a technique for construction of an special case of SGLMs which decreases the complexity of finding coefficients matrices.
http://bims.iranjournals.ir/article_484_e8bcd98926dd7174a8892e92e75c9438.pdf
General linear methods
Two--derivative methods
ordinary differential equation
Order conditions
A- and
L-stability
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
101
113
485
On the numerical solution of generalized Sylvester matrix equations
Amer Kaabi
kaabi_amer@kmsu.ac.ir
1
iran
The global FOM and GMRES algorithms are among the effective methods to solve Sylvester matrix equations. In this paper, we study these algorithms in the case that the coefficient matrices are real symmetric (real symmetric positive definite) and extract two CG-type algorithms for solving generalized Sylvester matrix equations. The proposed methods are iterative projection methods onto matrix Krylov subspaces. Numerical examples are presented.
http://bims.iranjournals.ir/article_485_1ba2c57bb65ad0afe866e7641b82604c.pdf
Generalized Sylvester matrix equations
Matrix Krylove subspace
Global gmres algorithm
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
115
124
486
An extension theorem for finite positive measures on surfaces of finite dimensional unit balls in Hilbert spaces
Ahmad Reza Soltani
soltani@kuc01.kuniv.edu.kw
1
Safieh Mahmoodi
mahmoodi@cc.iut.ac.ir
2
Kuwait University and Shiraz University
Isfahan University of Technology
A consistency criteria is given for a certain class of finite positive measures on the surfaces of the finite dimensional unit balls in a real separable Hilbert space. It is proved, through a Kolmogorov type existence theorem, that the class induces a unique positive measure on the surface of the unit ball in the Hilbert space. As an application, this will naturally accomplish the work of Kanter (1973) on the existence and uniqueness of the spectral measures of finite dimensional stable random vectors to the infinite dimensional ones. The approach presented here is direct and different from the functional analysis approach in Kuelbs (1973), Linde (1983) and the indirect approach of Tortrat (1976) and Dettweiler (1976).
http://bims.iranjournals.ir/article_486_e2f1c822857f6f622874900911e812f6.pdf
Extension Theorem
Separable Hilbert space
Finite Measures on
Surfaces of the Unit Balls
Stable distribution
Spectral measure
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
125
155
487
Embedding measure spaces
M.R. Koushesh
koushesh@cc.iut.ac.ir
1
Isfahan University of Technology
For a given measure space $(X,{mathscr B},mu)$ we construct all measure spaces $(Y,{mathscr C},lambda)$ in which $(X,{mathscr B},mu)$ is embeddable. The construction is modeled on the ultrafilter construction of the Stone--v{C}ech compactification of a completely regular topological space. Under certain conditions the construction simplifies. Examples are given when this simplification occurs.
http://bims.iranjournals.ir/article_487_5d8ac1365f2e598525cbe53890ad515d.pdf
Ultrafilter
thick subset
set of full outer measure
topological measure space
Baire measure
Stone--v{C}ech compactification
realcompactification
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
157
181
488
A class of Artinian local rings of homogeneous type
Leila Sharifan
leilasharifan@gmail.com
1
Hakim Sabzevari University, Sabzevar, Iran
Let $I$ be an ideal in a regular local ring $(R,n)$, we will find bounds on the first and the last Betti numbers of $(A,m)=(R/I,n/I)$. if $A$ is an Artinian ring of the embedding codimension $h$, $I$ has the initial degree $t$ and $mu(m^t)=1$, we call $A$ a {it $t-$extended stretched local ring}. This class of local rings is a natural generalization of the class of stretched local rings studied by Sally, Elias and Valla. For a $t-$extended stretched local ring, we show that ${h+t-2choose t-1}-h+1leq tau(A)leq {h+t-2choose t-1}$ and $ {h+t-1choose t}-1 leq mu(I) leq {h+t-1choose t}$. Moreover $tau(A)$ reaches the upper bound if and only if $mu(I)$ is the maximum value. Using these results, we show when $beta_i(A)=beta_i(gr_m(A))$ for each $igeq 0$. Beside, we will investigate the rigid behavior of the Betti numbers of $A$ in the case that $I$ has initial degree $t$ and $mu(m^t)=2$. This class is a natural generalization of {it almost stretched local rings} again studied by Elias and Valla. Our research extends several results of two papers by Rossi, Elias and Valla.
http://bims.iranjournals.ir/article_488_46a770dbf68f66aa47bf6509eded267f.pdf
artinian rings
Hilbert function
number of
generators
Cohen-Macaulay type
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
183
198
489
Stochastic bounds for a single server queue with general retrial times
Mohamed Boualem
robertt15dz@yahoo.fr
1
Natalia Djellab
djellab@yahoo.fr
2
Djamil Aïssani
lamos_bejaia@hotmail.com
3
University of Bejaia
University of Annaba
University of béjaia
We propose to use a mathematical method based on stochastic comparisons of Markov chains in order to derive performance indice bounds. The main goal of this paper is to investigate various monotonicity properties of a single server retrial queue with first-come-first-served (FCFS) orbit and general retrial times using the stochastic ordering techniques.
http://bims.iranjournals.ir/article_489_d8f721e663cfe851a582b1a8bde9e06e.pdf
Retrial queues
Markov chain
stochastic bounds
Monotonicity
ageing distributions
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
199
215
490
Existence and uniqueness of common coupled fixed point results via auxiliary functions
Sumit Chandok
chandhok.sumit@gmail.com
1
Erdal Karapinar
erdalkarapinar@yahoo.com
2
Mohammad Saeed Khan
mohammad@squ.edu.om
3
Khalsa College of Engineering & Technology (Punjab Technical University)
ATILIM UNIVERSITY
Sultan Qaboos University
The purpose of this paper is to establish some coupled coincidence point theorems for mappings having a mixed $g$-monotone property in partially ordered metric spaces. Also, we present a result on the existence and uniqueness of coupled common fixed points. The results presented in the paper generalize and extend several well-known results in the literature.
http://bims.iranjournals.ir/article_490_ff5cc3dca3e0121e2ecee853eea3a1ed.pdf
Coupled coincidence
point
ordered sets
Coupled fixed point
mixed monotone property
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
217
234
491
Relative volume comparison theorems in Finsler geometry and their applications
Bing Ye Wu
569405943@qq.com
1
Department of Mathematics
Minjiang University
We establish some relative volume comparison theorems for extremal volume forms of Finsler manifolds under suitable curvature bounds. As their applications, we obtain some results on curvature and topology of Finsler manifolds. Our results remove the usual assumption on S-curvature that is needed in the literature.
http://bims.iranjournals.ir/article_491_a6a751d01b68cc3adc7d1c13f8010dc7.pdf
extreme volume form
Finsler manifold
Gromov pre-compactness
first Betti number
fundamental group
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
235
242
492
An eigenvalue study on the sufficient descent property of a modified Polak-Ribière-Polyak conjugate gradient method
Saman Babaie-Kafaki
sbk@semnan.ac.ir
1
Semnan University
Based on an eigenvalue analysis, a new proof for the sufficient descent property of the modified Polak-Ribière-Polyak conjugate gradient method proposed by Yu et al. is presented.
http://bims.iranjournals.ir/article_492_329f84fb9fa3da162a1ea3377a2c650e.pdf
unconstrained optimization
Conjugate gradient algorithm
Sufficient descent condition
Eigenvalue
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
243
261
493
Various kinds of regular injectivity for $S$-posets
Leila Shahbaz
leilashahbaz@yahoo.com
1
Mojgan Mahmoudi
mojganmahmoudi@yahoo.com
2
University of Maragheh
Shahid Beheshti University
In this paper some properties of weak regular injectivity for $S$-posets, where $S$ is a pomonoid, are studied. The behaviour of different kinds of weak regular injectivity with products, coproducts and direct sums is considered. Also, some characterizations of pomonoids over which all $S$-posets are of some kind of weakly regular injective are obtained. Further, we give some Baer conditions which state the relation among some kinds of weak regular injectivity.
http://bims.iranjournals.ir/article_493_ffd4d4411686956bba1a760f8c5969b5.pdf
$S$-poset
regular injective
weakly regular injective
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
263
279
494
Implicit iteration approximation for a finite family of asymptotically quasi-pseudocontractive type mappings
Shuyi Zhang
jzzhangshuyi@126.com
1
Department of Mathematics, BoHai University
In this paper, strong convergence theorems of Ishikawa type implicit iteration process with errors for a finite family of asymptotically nonexpansive in the intermediate sense and asymptotically quasi-pseudocontractive type mappings in normed linear spaces are established by using a new analytical method, which essentially improve and extend some recent results obtained by Yang [Convergence theorems of implicit iteration process for asymptotically pseudocontractive mappings, Bulletin of the Iranian Mathematical Society, Available Online from 12 April 2011] and others.
http://bims.iranjournals.ir/article_494_3783b5bd681d2f9f26ad8b170b0d7dba.pdf
Normed linear spaces
implicit iteration process
asymptotically quasi-pseudocontractive type mappings
nonexpansive mappings
eng
Iranian Mathematical Society (IMS)
Bulletin of the Iranian Mathematical Society
1017-060X
1735-8515
2014-02-01
40
1
281
291
495
On the norm of the derived subgroups of all subgroups of a finite group
Zhencai Shen
zhencai688@sina.com
1
Shirong Li
shirong@sina.com
2
Wujie Shi
shiwujie@gmail.com
3
LMAM and School of Mathematical Sciences, Peking
University,
Beijing, 100871, China.
Guangxi University
Chongqing University of Arts and Sciences
In this paper, we give a complete proof of Theorem 4.1(ii) and a new elementary proof of Theorem 4.1(i) in [Li and Shen, On the intersection of the normalizers of the derived subgroups of all subgroups of a finite group, J. Algebra, 323 (2010) 1349--1357]. In addition, we also give a generalization of Baer's Theorem.
http://bims.iranjournals.ir/article_495_6dc0df68eafac1db15b433778ac7a5c1.pdf
Derived subgroup
solvable group
nilpotency class
Fitting length