Izumi Hasegawa
Hokkaido University of Education
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Publication
Featured researches published by Izumi Hasegawa.
Geometriae Dedicata | 2003
Izumi Hasegawa; Ion Mihai
Recently, B.-Y. Chen studied warped products which are CR-submanifolds in Kaehler manifolds and established general sharp inequalities for CR-warped products in Kaehler manifolds. In the present paper, we obtain a sharp inequality for the squared norm of the second fundamental form (an extrinsic invariant) in terms of the warping function for contact CR-warped products isometrically immersed in Sasakian manifolds. The equality case is considered. Also, the minimum codimension of a contact CR-warped product in an odd-dimensional sphere is determined.
Archive | 2016
Hitoshi Furuhata; Izumi Hasegawa
A statistical manifold is a smooth manifold equipped with a pair of a Riemannian metric and a torsion-free affine connection satisfying the Codazzi equation. We naturally have various dualistic geometric objects on it. In this article, the basics for statistical submanifolds in holomorphic statistical manifolds are given. We define the sectional curvature for a statistical structure, and study CR-submanifolds in a holomorphic statistical manifold of constant holomorphic sectional curvature. We prove that this sectional curvature of such a space vanishes if it admits a totally umbilical and a dual-totally umbilical generic submanifolds. Furthermore, we show that a Lagrangian submanifold is of constant sectional curvature if the statistical shape operator and its dual operator commute. Similarly, we generalize several theorems in the classical CR-submanifold theory.
Archive | 1996
Izumi Hasegawa; Kazunari Yamauchi; Hideo Shimada
Let M be an (m +1)-dimensional Finsler manifold with fundamental function L satisfying
Archive | 2003
Izumi Hasegawa; Kazunari Yamauchi
Scientiae Mathematicae japonicae | 2003
Izumi Hasegawa; Kazunari Yamauchi
L(x,ky) = kL(x,y),k >0
Journal of Geometry | 2017
Hitoshi Furuhata; Izumi Hasegawa; Yukihiko Okuyama; Kimitake Sato
Hokkaido Mathematical Journal | 1980
Izumi Hasegawa; Toshiyuki Nakane
(1.1) and
Journal of Geometry and Physics | 2017
Hitoshi Furuhata; Izumi Hasegawa; Yukihiko Okuyama; Kimitake Sato; Mohammad Shahid
Hokkaido Mathematical Journal | 2004
Izumi Hasegawa; Vasile Sorin Sabau; Hideo Shimada
rank\left( {{g_{ij}}} \right) = m + 1
Scientiae Mathematicae japonicae | 2003
Izumi Hasegawa; Kazunari Yamauchi