• Communications of the Korean Mathematical Society
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• 제22권2호
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• pp.289-295
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• 2007

We describe some conditions under which the product of two groups with certain property is a group with the same property, and we describe some conditions under which the product of hopfian manifolds is another hopfian manifold. As applications, we find some PL fibrators among the product of fibrators.

• Bulletin of the Korean Mathematical Society
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• 제40권1호
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• pp.63-76
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• 2003

In this article, we establish relations between the sectional curvature and the shape operator and also between the k-Ricci curvature and the shape operator for a slant submanifold in a Sasakian space form of constant $\varphi-sectional$ curvature with arbitrary codimension.

• Journal of the Korean Mathematical Society
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• 제42권4호
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• pp.827-845
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• 2005

In this paper, we present a general method for the stability analysis of some bursting models. Our method is geometric in the sense that we consider a flow-defined return map defined on a section and determine when the map is a contraction. We find that there are three different stability types in the codimension-1 planar bursters.

• Journal of the Korean Mathematical Society
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• 제37권4호
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• pp.503-519
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• 2000

It is well-known that an analytic generic CR submainfold M of codimension m in Cn+m is locally transformed by a biholomorphic mapping to a plane Cn$\times$Rm ⊂ Cn$\times$Cm whenever the Levi form L on M vanishes identically. We obtain such a normalizing biholomorphic mapping of M in terms of the defining function of M. Then it is verified without Frobenius theorem that M is locally foliated into complex manifolds of dimension n.

• Bulletin of the Korean Mathematical Society
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• 제43권4호
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• pp.841-846
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• 2006

Suppose that F is a closed t-aspherical PL n-manifold with finite, sparsely abelian ${\pi}_1(F)$ and A is a closed aspherical PL m-manifold with hopfian, normally cohopfian ${\pi}_1(A)$. If $X(F){\neq}0{\neq}X(A)$, then $F{\times}A$ is a codimension-(t+1) PL fibrator.

• Bulletin of the Korean Mathematical Society
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• 제49권3호
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• pp.445-454
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• 2012

On a closed, connected Riemannian manifold with a K$\ddot{a}$ahler foliation $\mathcal{F}$ of codimension $q$, any transverse Killing $r$-form ($2{\leq}r{\leq}q$) is parallel.

• The Pure and Applied Mathematics
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• 제16권1호
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• pp.31-46
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• 2009

In this paper we study the geometry of Einstein half light like submanifolds M of a Lorentz manifold ($\bar{M}$(c), $\bar{g}$) of constant curvature c, equipped with an integrable screen distribution on M such that the induced connection ${\nabla}$ is a metric connection and the operator $A_u$ is a screen shape operator.

• Honam Mathematical Journal
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• 제30권3호
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• pp.487-504
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• 2008

In this paper we study the geometry of codimension 2 screen conformal Einstein half lightiike submanifolds M of a semi-Riemannian manifold $(\={M}(c),\={g})$ of constant curvature c, with a Killing co-screen distribution on $\={M}$. The main result is a classification theorem for screen homothetic Einstein half lightlike submanifold of Lorentzian space forms.

• Kyungpook Mathematical Journal
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• 제53권3호
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• pp.333-340
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• 2013

In this paper, we prove that on a K$\ddot{a}$hler spin foliatoin of codimension $q=2n$, any eigenvalue ${\lambda}$ of type $r(r{\in}\{1,{\cdots},[\frac{n+1}{2}]\})$ of the basic Dirac operator $D_b$ satisfies the inequality ${\lambda}^2{\geq}\frac{r}{4r-2}\;{\inf}_M{\sigma}^{\nabla}$, where ${\sigma}^{\nabla}$ is the transversal scalar curvature of $\mathcal{F}$.

• Journal of the Korean Mathematical Society
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• 제44권4호
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• pp.799-807
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• 2007

In this paper we study non-simply connected Riemannian manifolds of constant positive curvature which have an orbit of codimension one under the action of a connected closed Lie subgroup of isometries. When the action is reducible we characterize the orbits explicitly. We also prove that in some cases the manifold is homogeneous.