Certain Conditions on the Ricci Tensor of Real Hypersurfaces in Quaternionic Projective Spaces

The purpose of this paper is to classify real hypersurfaces of quaternionic projective spaces whose Ricci tensor satisfy a pair of conditions on the maximal quaternionic distribution .     

Real Hypersurfaces of a Complex Projective Space in Terms of the Jacobi Operators

In this paper, we characterize some real hypersurfaces in a complex projective space CPn in terms of the shape operator A, the structure tensor and the Jacobi operator R.     

Ruled Real Hypersurfaces in a Nonflat Quaternionic Space Form

In this paper we construct many ruled real hypersurfaces in a nonflat quaternionic space form systematically, and in particular give an example of a homogeneous ruled real hypersurface in a quaternionic hyperbolic space. In the second half of this paper we characterize them by investigating the extrinsic shape of their geodesics. We also characterize curvature-adapted real hypersurfaces in nonflat quaternionic space forms from the same viewpoint.The first author was partially supported by Grant-in-Aid for Scientific Research (C) (No. 14540075), Ministry of Education, Science, Sports and Culture.The second author was partially supported by Grant-in-Aid for Scientific Research (C) (No. 14540080), Ministry of Education, Science, Sports and Culture.     

Moduli of Quaternionic Superminimal Immersions of 2-Spheres into Quaternionic Projective Spaces

The aim of this paper is to describe the moduli spaces of degree d quaternionic superminimal maps from 2-spheres to quaternionic projective spaces HPn. We show that such moduli spaces have the structure of projectivized fibre products and are connected quasi-projective varieties of dimension 2nd + 2n + 2. This generalizes known results for spaces of harmonic 2-spheres in S⁴.     

Real Hypersurfaces in Quaternionic Space Forms Satyisfying Axioms of Planes

A Riemannian manifold satisfies the axiom of 2-planes if at each point, there are suficiently many totally geodesic surfaces passing through that point. Real hypersurfaces in quaternionic space forms admit nice families of tangent planes, namely, totally real, half-quaternionic and quaternionic. Several definitions of axiom of planes arise naturally when we consider such families of tangent planes. We are able to classify real hypersurfaces in quaternionic space forms satisfying these definitions.     

The Varieties of Tangent Lines to Hypersurfaces in Projective Spaces

For a hypersurface in a projective space, we consider the set of pairs of a point and a line in the projective space such that the line intersects the hypersurface at the point with a fixed multiplicity. We prove that this set of pairs forms a smooth variety for a general hypersurface.     

复射影空间的实2-调和超曲面

本文研究了复射影空间中的实２－调和超曲面和实极小超曲面之间的关系,推广了Ｌａｗｓｏｎ Ｈ．Ｂ和Ｋｏｎ Ｍ．关于实极小超曲面的Ｐｉｎｃｈｉｎｇ结果     

Some Functions of Points in Projective Spaces

Extending earlier results in the plane, we prove that every n-polygon in sufficiently general position in d-dimensional projective space, n d + 2, gives rise to a derived n-polygon, which preserves a few functions; these functions are the cyclial product of (actually affine) ratios of various points, obtained by proper projections on suitable lines.     

非平坦的Randers空间中的极小旋转超曲面

本文的研究分为两部分.第一部分是在特殊的Randers空间中得到了等距浸入的HT-极小旋转超曲面,这些特殊的Rander空间是非Minkowski的,但是它们的旗曲率为零.第二部分刻画了Funk空间中的各向异性极小旋转超曲面.     

Geometry of Holomorphic Distributions of Real Hypersurfaces in a Complex Projective Space

We characterize homogeneous real hypersurfaces M's of type (A ₁), (A ₂) and (B) of a complex projective space in the class of real hypersurfaces by studying the holomorphic distribution T ⁰ M of M.     

Invariant Metrizability and Projective Metrizability on Lie Groups and Homogeneous Spaces

In this paper, we study the invariant metrizability and projective metrizability problems for the special case of the geodesic spray associated to the canonical connection of a Lie group. We prove that such canonical spray is projectively Finsler metrizable if and only if it is Riemann metrizable. This result means that this structure is rigid in the sense that considering left invariant metrics, the potentially much larger class of projective Finsler metrizable canonical sprays, corresponding to Lie groups, coincides with the class of Riemann metrizable canonical sprays. Generalisation of these results for geodesic orbit spaces are given.

     

复射影空间和四元数射影空间中广义赤道的一个新特征

本文研究复射影空间ＣＰ＾ｎ和四元数射影空间ＱＰ＾ｎ中的紧致极小超曲面，对其上Ｊａｃｏｂｉ算子的最小特征值给出了一个最佳上界估计，由此给出了ＣＰ＾ｎ和ＱＰ＾ｎ中广义赤道的一个新的特征。     

Real Hypersurfaces with Two Principal Curvatures in Complex Projective and Hyperbolic Planes

We find the first examples of real hypersurfaces with two nonconstant principal curvatures in complex projective and hyperbolic planes, and we classify them. It turns out that each such hypersurface is foliated by equidistant Lagrangian flat surfaces with parallel mean curvature or, equivalently, by principal orbits of a cohomogeneity two polar action.     

射影空间中代数曲线与超曲面的一些新的性质

发现了代数曲线的新的不变量一特征数,并得到了Pascal定理的不同于3次曲线的Cllasles定理和高次曲线中的Cayley-Bacharach定理等形式的高次推广.进一步研究了平面代数曲线的一些性质.通过定义m次Pascal超曲面,将Pascal定理推广到n维射影空间的m次超曲面中,证明了n-单纯形上的Pascal点位于一个m次Pascal超曲面的充要条件是其每个2维面上的Pascal点分别位于m次平面Pascal空间的一条代数曲线上.进一步,给出了一定条件下m次Pascal超曲面与m-1次Pascal超曲面之间的内在关系.     

Orbits of Real Semisimple Lie Groups on Real Loci of Complex Symmetric Spaces

Let G be a complex semisimple algebraic group and X be a complex symmetric homogeneous G-variety. Assume that both G, X as well as the G-action on X are defined over real numbers.Then G(R) acts on X(R) with finitely many orbits. We describe these orbits in combinatorial terms using Galois cohomology, thus providing a patch to a result of Borel and Ji.     

Some Comments on Projective Quadrics Subordinate to Pseudo-Hermitian Spaces

We study in some detail the structure of the projective quadric Q′ obtained by taking the quotient of the isotropic cone in a standard pseudo-hermitian space H _p,q with respect to the positive real numbers \mathbb R⁺{\mathbb R^{+}} and, further, by taking the quotient [(Q)\tilde] = Q￠/U(1){\tilde Q = Q^\prime /U(1)}. The case of signature (1, 1) serves as an illustration. Q̃ is studied as a compactification of \mathbb R ×H_p-1,q-1{\mathbb R \times H_{p-1,q-1}}     

Isometries of Quaternionic Lie Groups

We study connected Lie groups whose Lie algebra is obtained as the tensor product of a real associative algebra and the algebra of quaternions. It is proved that they carry a natural integrable -structure. We endow such quaternionic Lie groups with a left-invariant Hermitian metric and study the identity connected component of their isometry groups. The determination of such identity connected component is illustrated with a family of examples.     

On Some Categories and Functors in the Theory of Quaternionic Bergman Spaces

Basic facts are presented about the theory of quaternionic Bergman spaces with special emphasis on what is happening with them under conformal transformations of the domains. Constructing a series of categories of quaternion-valued functions as well as functors acting between them we show that the arising spaces and operators have conformally covariant or invariant characters in terms of the theory of categories. The second-named and the third-named authors were partially supported by CONACYT projects as well as by IPN in the framework of COFAA and SIP programs.     

Estimates of Derivatives in Sobolev Spaces in Terms of Hypergeometric Functions

Mathematical Notes - The paper deals with sharp estimates of derivatives of intermediate order $$kle n-1$$ in the Sobolev space $$mathring W^n_2[0;1]$$ , $$ninmathbb N$$ . The functions...