• 대한수학회보
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• 제55권3호
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• pp.871-879
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• 2018

The purpose of the present paper is to study on nearly $paraK{\ddot{a}}hler$ manifolds. Firstly, to investigate some properties of the Ricci tensor and the $Ricci^*$ tensor of nearly $paraK{\ddot{a}}hler$ manifolds. Secondly, to define a special metric connection with torsion on nearly $paraK{\ddot{a}}hler$ manifolds and present its some properties.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제20권3호
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• pp.199-206
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• 2013

We present a 4-dimensional nil-manifold as the first example of a closed non-K$\ddot{a}$hlerian symplectic manifold with the following property: a function is the scalar curvature of some almost K$\ddot{a}$hler metric iff it is negative somewhere. This is motivated by the Kazdan-Warner's work on classifying smooth closed manifolds according to the possible scalar curvature functions.

• 대한수학회지
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• 제52권3호
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• pp.587-601
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• 2015

In this paper, we investigate the $\mathbb{R}$-complex Hermitian Finsler spaces, emphasizing the differences that separate them from the complex Finsler spaces. The tools used in this study are the Chern-Finsler and Berwald connections. By means of these connections, some classes of the $\mathbb{R}$-complex Hermitian Finsler spaces are defined, (e.g. weakly K$\ddot{a}$hler, K$\ddot{a}$hler, strongly K$\ddot{a}$hler). Here the notions of K$\ddot{a}$hler and strongly K$\ddot{a}$hler do not coincide, unlike the complex Finsler case. Also, some kinds of Berwald notions for such spaces are introduced. A special approach is devoted to obtain the equivalence conditions for an $\mathbb{R}$-complex Hermitian Finsler space to become a weakly Berwald or Berwald. Finally, we obtain the conditions under which an $\mathbb{R}$-complex Hermitian Finsler space with Randers metric is Berwald. We get some clear examples which illustrate the interest for this work.

• Korean Journal of Mathematics
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• 제5권1호
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• pp.75-82
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• 1997

We show that the normal bundle of a Lagrangian submanifold in a K$\ddot{a}$hler manifold has a symplectic structure and provide the equivalent conditions for the normal bundle of such to be K$\ddot{a}$hler.

• 대한수학회지
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• 제55권4호
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• pp.963-974
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• 2018

We discuss two kinds of almost contact metric structures on a one-parameter family of totally umbilical hyperspheres in the nearly $K{\ddot{a}}hler$ unit 6-sphere $S^6$.

• Korean Journal of Mathematics
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• 제21권4호
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• pp.473-481
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• 2013

We discuss on the classification problem of symplectic manifolds into three families according to the scalar curvature functions of almost K$\ddot{a}$hler metrics they admit. We also present a 4-dimensional solv-manifold as an example which belongs to one of the three families.

• 대한수학회논문집
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• 제29권4호
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• pp.549-554
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• 2014

We present a smooth simply connected closed eight dimensional manifold with distinct symplectic deformation equivalence classes [[${\omega}_i$]], i = 1, 2 such that the symplectic Z invariant, which is defined in terms of the scalar curvatures of almost K$\ddot{a}$hler metrics in [5], satisfies $Z(M,[[{\omega}_1]])={\infty}$ and $Z(M,[[{\omega}_2]])$ < 0.

• 대한수학회논문집
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• 제25권3호
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• pp.451-456
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• 2010

In this paper, we construct explicitly K$\ddot{a}$hler metrics on the ellipsoids and calculate their sectional curvatures. Using MAPLE [3], we obtain some geodesic curves on an ellipsoid so that if some conditions are dropped in Question 2.1 [4], then Question 2.1 is not true.

• 호남수학학술지
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• 제35권2호
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• pp.119-128
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• 2013

In the present paper, we define a product-symmetric recurrent-metric connection in an almost Hermitian manifold and study some properties of this connection, in particular, its curvature properties.

• 대한수학회보
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• 제52권3호
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• pp.1027-1034
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• 2015

As a natural generalization of the contact metric manifolds, Kim, Park and Sekigawa discussed quasi contact metric manifolds based on the geometry of the corresponding quasi $K{\ddot{a}}hler$ cones. In this paper, we show that a quasi contact metric manifold is a contact manifold.