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Communications of the Korean Mathematical Society
Journal Basic Information
pISSN :
1225-1763
eISSN :
2234-3024
Journal DOI :
10.4134/CKMS
Frequency :
Others
Publisher:
The Korean Mathematical Society
Editor in Chief :
Volume & Issues
Volume 13, Issue 4 - Oct 1998
Volume 13, Issue 3 - Jul 1998
Volume 13, Issue 2 - Apr 1998
Volume 13, Issue 1 - Jan 1998
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1
ON LEFT REGULAR po-SEMIGROUPS
Lee, Sang-Keun ; Jung, Jae-Hong ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 1~6
Abstract
The paper refers to ordered semigroups in which $x^2 (x \in S)$ are left ideal elements. We mainly show that this $po$-semigroup is left regular if and only if S is a union of left simple subsemigroups of S.
2
ISOMORPHISMS OF $B{(n)}_{2n}$
Kang, J.H ; Jo, Y.S ; Park, K.S ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 7~20
Abstract
In this paper, we will investigated certain two types of isomorphisms of $B^{(n)}_{2n}$ which are closely related.
3
A STRUCTURE THEOREM FOR
-HYPONORMAL CONTRACTIONS
Lee, Mi-Young ; Lee, Sang-Hun ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 21~27
Abstract
In this paper we prove a structure theorem for p-hyponomal contractions and also give an example of a p-hyponormal operator which is not *-paranormal.
4
JONES' INDEX FOR FIXED POINT ALGEBRAS
Lee, Jung-Rye ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 29~36
Abstract
We show that if M is a $II_1$-factor and a countable discrete group G acts outerly on M then Jones' index $[M:M^G]$ of a pair of $II_1^-factors is equal to the order
G
of G. It is also shown that for a subgroup H of G Jones' index $[M^H:M^G]$ is equal to the group index [G:H] under certain conditions.
5
THE RIEMANN PROBLEM FOR A SYSTEM OF CONSERVATION LAWS OF MIXED TYPE (II)
Lee, Choon-Ho ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 37~59
Abstract
We prove that solutions $u^\epsilon$ for the mixed hyperbolic-elliptic system of conservation laws with the viscosity term are total variation bounded uniformly in $\epsilon$ and that the solution $u^\epsilon$ converges to the solution for the mixed hyperbolic-elliptic Riemann problem as $\epsilon \to 0$.
6
DISCRETE PROOF OF EVEN KAKUTANI EQUIVALENCE VIA
- AND ,
-EQUIVALENCE
Park, Kye-Won ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 61~72
Abstract
It has been known that if T and S are even Kakutani equivalent, then there exists U such that T and U are $\alpha$-equivalent and S and U are $\beta$-equivalent where $\alpha$ and $\beta$ are irrationally related. In this paper we give a complete discrete proof of this theorem without using R-actions.
7
UNSOLVABILITY OF SOME PARTIAL DIFFERENTIAL OPERATOR
Kim, Rak-Joong ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 73~76
Abstract
It is proved that the partial differential operator $D_x + ix^q D^2_y$ is not locally solvable in any open set which intersects the line x = 0, when $q = - \frac{2l-1}{2k-1}$ is not an integer.
8
SEMI-QUASITRIANGULARITY OF TOEPLITZ OPERATORS WITH QUASICONTINUOUS SYMBOLS
Kim, In-Hyoun ; Lee, Woo-Young ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 77~84
Abstract
In this note we show that if $T_{\varphi}$ is a Toeplitz operator with quasicontinuous symbol $\varphi$, if $\omega$ is an open set containing the spectrum $\sigma(T_\varphi)$, and if $H(\omega)$ denotes the set of analytic fuctions defined on $\omege$, then the following statements are equivalent: (a) $T_\varphi$ is semi-quasitriangular. (b) Browder's theorem holds for $f(T_\varphi)$ for every $f \in H(\omega)$. (c) Weyl's theorem holds for $f(T_\varphi)$ for every $f \in H(\omega)$. (d) $\sigma(T_{f \circ \varphi}) = f(\sigma(T_varphi))$ for every $f \in H(\omega)$.
9
ON SOME CR-SUBMANIFOLDS OF (n-1) CR-DIMENSION IN A COMPLEX PROJECTIVE SAPCE
Kwon, Jung-Hwan ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 85~94
Abstract
The purpose of this paper is to give sample characterizations of n-dimensional CR-submanifolds of (n-1) CR-semifolds of (n-1) CR-dimension immersed in a complex projective space $CP^{(n+p)/2}$ with Fubini-Study metric and we study an n-dimensional compact, orientable, minimal CR-submanifold of (n-1) CR-dimension in $CP^{(n+p)/2}$.
10
IDEAL BOUNDARY OF CAT(0) SPACES
Jeon, Myung-Jin ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 95~107
Abstract
In this paper we prove the Hopf-Rinow theorem for CAT(0) spaces and show that the ideal boundaries of complete CAT(0) manifolds of dimension 2 or 3 with some additional conditions are homeomorphic to the circle or 2-sphere by the characterization of the local shadows around the branch points.
11
REMARKS ON THE REIDEMEISTER NUMBERS FOR COINCIDENCE
Seoung Ho Lee ; Sung Do Baek ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 109~121
Abstract
Let X,Y be connected, locally connected, semilocally simply connected and $f,g : X \to Y$ be a pair of maps. We find an upper bound of the Reidemeister number R(f,g) by using the regular coverig spaces.
12
SOME DYNAMICAL PROPERTIES OF A WEAKLY ALMOST PERIODIC FLOW
Song, Hyung-Soo ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 123~129
Abstract
In this paper, we study some dynamical properties of a weakly almost periodic flow. In particular we get, in a weakly almost periodic flow (X,T), the groups I and A(I) of all automorphisms of I are isomorphic, where E(X) is the enveloping semigroup of (X,T) and I is the minimal right ideal in E(X).
13
F-PROXIMAL FLOWS
Kim, Young-Key ; Byun, Hee-Young ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 131~136
Abstract
The proximal flow have been introduced and studied by J. Auslander [1] and R. Ellis [2]. S. Glasner showed the various properties of the proximal flow in [7]. S. K. Kaul [3] have introduced the first prolongation set which contains the orbit closure. We define the F-proximal flow and $FP_\pi(y)$ by using the first prolongation set and investigated its properties.
14
On fuzzy FC-compactness
In, Byung-Sik ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 137~150
Abstract
The purpose of this paper is to introduce and study the concept of fuzzy FC-compactness for fuzzy topological spaces.
15
ON THE STRONG LAW OF LARGE NUMBERS FOR LINEARLY POSITIVE QUADRANT DEPENDENT RANDOM VARIABLES
Kim, Tae-Sung ; Seo, Hye-Young ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 151~158
Abstract
In this note we derive inequalities of linearly positive quadrant dependent random variables and obtain a strong law of large numbers for linealy positive quardant dependent random variables. Our results imply an extension of Birkel's strong law of large numbers for associated random variables to the linear positive quadrant dependence case.
16
A SUBMARTINGALE INEQUALITY
Kim, Young-Ho ; Kim, Byung-Il ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 159~170
Abstract
In this paper, we extend Burkholder's exponential inequality for a strong subordinate of a nonnegative bounded submartingale.
17
CONVERGENCE OF NONLINEAR SEMIGROUPS IN A HYPERBOLIC SPACE
Lee, Young-S. ; Park, Sang-Don ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 171~179
Abstract
In this paper, we establish Trotted-Kato type convergence theoren for nonlinear semigroups generated by coaccretive operators in a hyperbolic space.
18
ON THE GIBBS PHENOMENON FOR THE SHANNON SAMPLING SERIES IN WAVELET SUBSPACES AND A WAY TO GO AROUND
Shim, Hong-Tae ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 181~193
Abstract
The Shannon sampling series is the prototype of an interpolating series or sampling series. Also the Shannon wavelet is one of the protypes of wavelets. But the coefficients of the Shannon sampling series are different function values at the point of discontinuity, we analyze the Gibbs phenomenon for the Shannon sampling series. We also find a way to go around this overshoot effect.
19
ITERATION METHOD FOR CONSTRAINED OPTIMIZATION PROBLEMS GOVERNED BY PDE
Lee, Hyung-Chun ;
Communications of the Korean Mathematical Society, volume 13, issue 1, 1998, Pages 195~209
Abstract
In this paper we present a new iteration method for solving optimization problems governed by partial differential equations. We generalize the existing methods such as simple gradient methods and pseudo-time methods to get an efficient iteration method. Numerical tests show that the convergence of the new iteration method is much faster than those of the pseudo-time methods especially when the parameter $\sigma$ in the cost functional is small.