• Korean Journal of Mathematics
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• v.13 no.1
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• pp.51-59
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• 2005

Let (M, $g$) be a compact oriented self-dual 4-dimensional Einstein manifold with positive sectional curvature. Then we show that, up to rescaling and isometry, (M, $g$) is $S^4$ or $\mathbb{C}\mathbb{P}_2$, with their cannonical metrics.

• Bulletin of the Korean Mathematical Society
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• v.41 no.3
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• pp.413-418
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• 2004

Invertible and isometric composition operators acting on vector-valued Hardy space $H^2$(E) are characterized.

• Communications of the Korean Mathematical Society
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• v.10 no.1
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• pp.137-143
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• 1995

First we recall some properties of the spaces $D_p$ and study the continuity of the operators on $D_p$. We also consider the continuity of the operations on the dual spaces $D'_p$ with the weak topology.

• Bulletin of the Korean Mathematical Society
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• v.51 no.4
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• pp.1005-1013
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• 2014

Let ${\phi}$ be an analytic self map of the open unit disc D. In this paper, we study the composition operator $C_{\phi}$ from the Bergman space on D to the Hardy space on D.

• Korean Journal of Mathematics
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• v.23 no.1
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• pp.199-203
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• 2015

In this paper we give an example which is a weakly subnormal weighted shift but not 2-hyponormal. Also, we show that every partially normal extension of an isometry T needs not be 2-hyponormal even though p.n.e.(T) is weakly subnormal.

• Communications of the Korean Mathematical Society
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• v.18 no.1
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• pp.1-20
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• 2003

본 요약논문에서는 단순 연결된 리만곡면들의 isometry군, 그 군의 이산부분군을 이용한 리 만곡면들의 tessellation 그리고 regular map에 대해 소개하고 그 응용과 상호연관성들에 대해 살펴본다. 그리고, 여러가지 관점에서의 regular map의 분류에 대해 소개하고, 최근까지 연구되어진 바에 대해 정리해 보고자 한다.

• Bulletin of the Korean Mathematical Society
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• v.40 no.1
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• pp.9-15
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• 2003

In this paper, we will deal with the Aleksandrov-Rassias problem. More precisely, we prove some theorems concerning the mappings preserving one or two distances.

• Bulletin of the Korean Mathematical Society
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• v.55 no.5
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• pp.1433-1440
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• 2018

We study the polarity of cohomogeneity two isometric actions on Riemannian manifolds of constant negative curvature.

• Journal of the Korean Mathematical Society
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• v.56 no.6
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• pp.1489-1502
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• 2019

This paper describes when a partial isometry satisfies several weak normal properties. Topics treated include quasi-normality, subnormality, hyponormality, p-hyponormality (p > 0), w-hyponormality, paranormality, normaloidity, spectraloidity, the von Neumann property and Weyl's theorem.

• Bulletin of the Korean Mathematical Society
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• v.59 no.2
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• pp.351-360
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• 2022

We prove that a punctured-torus group of hyperbolic 4-space which keeps an embedded hyperbolic 2-plane invariant has a strictly parabolic commutator. More generally, this rigidity persists for a punctured-surface group.