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Bulletin of the Korean Mathematical Society
Journal Basic Information
pISSN :
1015-8634
eISSN :
2234-3016
Journal DOI :
10.4134/BKMS
Frequency :
Others
Publisher:
The Korean Mathematical Society
Editor in Chief :
Volume & Issues
Volume 43, Issue 4 - Nov 2006
Volume 43, Issue 3 - Aug 2006
Volume 43, Issue 2 - May 2006
Volume 43, Issue 1 - Feb 2006
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1
ON THE RANGE CLOSURE OF AN ELEMENTARY OPERATOR
Canavati Jose Angel ; Djordjevic Slavisa V. ; Duggal Bhagwati Prasad ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 671~677
DOI : 10.4134/BKMS.2006.43.4.671
Abstract
Let
be Hilbert space contractions, and let
be the elementary operator
. A number of conditions which are equivalent to '
has closed range' are proved.
2
THE CRITICAL POINT EQUATION ON A FOUR DIMENSIONAL WARPED PRODUCT MANIFOLD
Hwang, Seung-Su ; Chang, Jeong-Wook ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 679~692
DOI : 10.4134/BKMS.2006.43.4.679
Abstract
On a compact oriented n-dimensional manifold
, it has been conjectured that a metric g satisfying the critical point equation (2) should be Einstein. In this paper, we prove that if a manifold
is a 4-dimensional oriented compact warped product, then g can not be a solution of CPE with a non-zero solution function f.
3
MULTIPLICITY RESULTS FOR A CLASS OF SECOND ORDER SUPERLINEAR DIFFERENCE SYSTEMS
Zhang, Guoqing ; Liu, Sanyang ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 693~701
DOI : 10.4134/BKMS.2006.43.4.693
Abstract
Using Minimax principle and Linking theorem in critical point theory, we prove the existence of two nontrivial solutions for the following second order superlinear difference systems
where T is a positive integer, [1, T] is the discrete interval {1, 2,..., T},
is the forward difference operator and
.
4
JENSEN TYPE QUADRATIC-QUADRATIC MAPPING IN BANACH SPACES
Park, Choon-Kil ; Hong, Seong-Ki ; Kim, Myoung-Jung ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 703~709
DOI : 10.4134/BKMS.2006.43.4.703
Abstract
Let X, Y be vector spaces. It is shown that if an even mapping
satisfies f(0) = 0 and
for all x, y, z
X, then the mapping
is quadratic. Furthermore, we prove the Cauchy-Rassias stability of the functional equation (0.1) in Banach spaces.
5
STRONG COMMUTATIVITY PRESERVING MAPPINGS ON SEMIPRIME RINGS
Ali, Asif ; Yasen, Muhammad ; Anwar, Matloob ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 711~713
DOI : 10.4134/BKMS.2006.43.4.711
Abstract
Let R be a semiprime ring and f be an endomorphism on R. If f is a strong commutativity preserving (simply, scp) map on a non-zero ideal U of R, then f is commuting on U.
6
ON WEIGHTED WEYL SPECTRUM, II
Arora Subhash Chander ; Dharmarha Preeti ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 715~722
DOI : 10.4134/BKMS.2006.43.4.715
Abstract
In this paper, we show that if T is a hyponormal operator on a non-separable Hilbert space H, then
, where
is the weighted Weyl spectrum of weight a with
. We also give some conditions under which the product of two
operators is
and its converse implication holds, too. Finally, we show that the weighted Weyl spectrum of a hyponormal operator satisfies the spectral mapping theorem for analytic functions under certain conditions.
7
FREE CYCLIC CODES OVER FINITE LOCAL RINGS
Woo, Sung-Sik ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 723~735
DOI : 10.4134/BKMS.2006.43.4.723
Abstract
In [2] it was shown that a 1-generator quasi-cyclic code C of length n = ml of index l over
is free if C is generated by a polynomial which divides
. In this paper, we prove that a necessary and sufficient condition for a cyclic code over
of length m to be free is that it is generated by a polynomial which divides
. We also show that this can be extended to finite local rings with a principal maximal ideal.
8
ON THE STABILITY OF INVOLUTIVE A-QUADRATIC MAPPINGS
Park, Won-Gil ; Bae, Jae-Hyeong ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 737~745
DOI : 10.4134/BKMS.2006.43.4.737
Abstract
In this paper, we will investigate the Hyers-Ulam stability of an involutive A-quadratic mapping.
9
FUGLEDE-PUTNAM THEOREM FOR p-HYPONORMAL OR CLASS y OPERATORS
Mecheri, Salah ; Tanahashi, Kotaro ; Uchiyama, Atsushi ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 747~753
DOI : 10.4134/BKMS.2006.43.4.747
Abstract
We say operators A, B on Hilbert space satisfy Fuglede-Putnam theorem if AX = X B for some X implies
. We show that if either (1) A is p-hyponormal and
is a class y operator or (2) A is a class y operator and
is p-hyponormal, then A, B satisfy Fuglede-Putnam theorem.
10
ON THE FLATNESS AND INJECTIVITY OF DUAL MODULES (III)
Huang, Zhaoyong ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 755~762
DOI : 10.4134/BKMS.2006.43.4.755
Abstract
For a commutative ring R and an injective cogenerator E in the category of R-modules, we characterize von Neumann regular rings and semisimple artinian rings in terms of the properties of dual modules with respect to E.
11
ON THE PROJECTIVE FOURFOLDS WITH ALMOST NUMERICALLY POSITIVE CANONICAL DIVISORS
Fukuda, Shigetaka ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 763~770
DOI : 10.4134/BKMS.2006.43.4.763
Abstract
Let X be a four-dimensional projective variety defined over the field of complex numbers with only terminal singularities. We prove that if the intersection number of the canonical divisor K with every very general curve is positive (K is almost numerically positive) then every very general proper subvariety of X is of general type in ';he viewpoint of geometric Kodaira dimension. We note that the converse does not hold for simple abelian varieties.
12
ITERATIVE ALGORITHMS WITH ERRORS FOR NONEXPANSIVE MAPPINGS IN BANACH SPACES
Jung, Jong-Soo ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 771~790
DOI : 10.4134/BKMS.2006.43.4.771
Abstract
The iterative algorithms with errors for nonexpansive mappings are investigated in Banach spaces. Strong convergence theorems for these algorithms are obtained. Our results improve the corresponding results in [5, 13-15, 23, 27-29, 32] as well as those in [1, 16, 19, 26] in framework of a Hilbert space.
13
DISCUSSION ON THE ANALYTIC SOLUTIONS OF THE SECOND-ORDER ITERATED DIFFERENTIAL EQUATION
Liu, HanZe ; Li, WenRong ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 791~804
DOI : 10.4134/BKMS.2006.43.4.791
Abstract
This paper is concerned with a second-order iterated differential equation of the form
with the distinctive feature that the argument of the unknown function depends on the state. By constructing a convergent power series solution of an auxiliary equation, analytic solutions of the original equation are obtained.
14
COMMUTATOR LENGTH OF SOLVABLE GROUPS SATISFYING MAX-N
Mehri, Akhavan-Malayeri ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 805~812
DOI : 10.4134/BKMS.2006.43.4.805
Abstract
In this paper we find a suitable bound for the number of commutators which is required to express every element of the derived group of a solvable group satisfying the maximal condition for normal subgroups. The precise formulas for expressing every element of the derived group to the minimal number of commutators are given.
15
STATIONARITY AND β-MIXING PROPERTY OF A MIXTURE AR-ARCH MODELS
Lee, Oe-Sook ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 813~820
DOI : 10.4134/BKMS.2006.43.4.813
Abstract
We consider a MAR model with ARCH type conditional heteroscedasticity. MAR-ARCH model can be derived as a smoothed version of the double threshold AR-ARCH model by adding a random error to the threshold parameters. Easy to check sufficient conditions for strict stationarity,
property and existence of moments of the model are given via Markovian representation technique.
16
DEGENERATE PRINCIPAL SERIES FOR EXCEPTIONAL p-ADIC GROUPS OF TYPE G
_{2}
Choi, Seun-Gil ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 821~829
DOI : 10.4134/BKMS.2006.43.4.821
Abstract
We determine reducibility points of degenerate principal series for exceptional p-adic groups of type
via Jacquet module techniques and Hecke algebra isomorphisms
17
BOEHMIANS ON THE TORUS
Nemzer, Dennis ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 831~839
DOI : 10.4134/BKMS.2006.43.4.831
Abstract
By relaxing the requirements for a sequence of functions to be a delta sequence, a space of Boehmians on the torus
is constructed and studied. The space
contains the space of distributions as well as the space of hyperfunctions on the torus. The Fourier transform is a continuous mapping from
onto a subspace of Schwartz distributions. The range of the Fourier transform is characterized. A necessary and sufficient condition for a sequence of Boehmians to converge is that the corresponding sequence of Fourier transforms converges in
.
18
PL FIBRATORS AMONG PRODUCTS OF HOPFIAN MANIFOLDS
Jeoung, Chang-Sik ; Kim, Yong-Kuk ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 841~846
DOI : 10.4134/BKMS.2006.43.4.841
Abstract
Suppose that F is a closed t-aspherical PL n-manifold with finite, sparsely abelian
and A is a closed aspherical PL m-manifold with hopfian, normally cohopfian
. If
, then
is a codimension-(t+1) PL fibrator.
19
MODIFIED ISHIKAWA ITERATIVE SEQUENCES WITH ERRORS FOR ASYMPTOTICALLY SET-VALUED PSEUCOCONTRACTIVE MAPPINGS IN BANACH SPACES
Kim, Jong-Kyu ; Nam, Young-Man ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 847~860
DOI : 10.4134/BKMS.2006.43.4.847
Abstract
In this paper, some new convergence theorems of the modified Ishikawa and Mann iterative sequences with errors for asymptotically set-valued pseudocontractive mappings in uniformly smooth Banach spaces are given.
20
A NOTE ON A CHOQUET-DENY-TYPE THEOREM
Kashimoto Marcia Sayuri ; Prolla Joao Bosco ;
Bulletin of the Korean Mathematical Society, volume 43, issue 4, 2006, Pages 861~868
DOI : 10.4134/BKMS.2006.43.4.861
Abstract
We present a Choquet-Deny-type theorem for downward filtering convex sets of continuous functions and show that the Identity Korovkin cone of a downward filtering convex cone S is exactly the uniform closure of S.