Submanifolds With Homothetic Gauss Map In Codimension Two

高余维球面中极小子流形的刚性

Rigidity of Minimal Submanifolds in Spheres of Higher Codimension

该研究针对单位球面中高余维极小子流形的陈省身猜想，建立积分不等式并在第二基本形式平方模长挤压条件下获新刚性定理，推进了极小子流形刚性研究。

Topological obstructions for submanifolds in low codimension

We prove integral curvature bounds in terms of the Betti numbers for compact submanifolds of the Euclidean space with low codimension. As an application, we obtain topological obstructions for $δ$-pinched immersions. Furthermore, we obtain intrinsic obstructions for minimal submanifolds in spheres with pinched second fundamental form.

Deforming submanifolds of arbitrary codimension in a sphere

In this paper, we prove some convergence theorems for the mean curvature flow of closed submanifolds in the unit sphere $\mathbb{S}^{n+d}$ under integral curvature conditions. As a consequence, we obtain several differentiable sphere theorems for certain submanifolds in $\mathbb{S}^{n+d}$.

Curvature estimates for minimal submanifolds of higher codimension and small G-rank

We obtain new curvature estimates and Bernstein type results for minimal $n-$submanifolds in $\ir{n+m},\, m\ge 2$ under the condition that the rank of its Gauss map is at most 2. In particular, this applies to minimal surfaces in Euclidean spaces of arbitrary codimension.

Submanifolds of codimension two attaining equality in an extrinsic inequality

We provide a parametric construction in terms of minimal surfaces of the Euclidean submanifolds of codimension two and arbitrary dimension that attain equality in an inequality due to De Smet, Dillen, Verstraelen and Vrancken. The latter involves the scalar curvature, the norm of the normal curvature tensor and the length of the mean curvature vector.

Harmonic Gauss maps of submanifolds of arbitrary codimension of the Euclidean space and sphere and some applications

It is proved some results about existence and non existence of unit normal sections of submanifolds of the Euclidean space and sphere which associated Gauss maps are harmonic. Some applications to CMC hypersurfaces of the sphere and isoparametric submanifolds are obtained too.

高码维平均曲率流：具有一个时空码维的类空凸子流形

High codimension mean curvature flow of spacelike-convex submanifolds with one spacelike codimension

研究伪欧氏空间中高码维类空子流形的平均曲率流，证明初始紧致类空凸子流形在流下曲率收缩和非坍缩量保持，并证明Huisken和Gage-Hamilton定理的类比结果。

A spherical Bernstein theorem for minimal submanifolds of higher codimension

Combining the tools of geometric analysis with properties of Jordan angles and angle space distributions, we derive a spherical and a Euclidean Bernstein theorem for minimal submanifolds of arbitrary dimension and codimension, under the condition that the Gauss image is contained in some geometrically defined closed region of a Grassmannian manifold. The proof depends on the subharmoncity of an auxiliary function, the Codazzi equations and geometric measure theory.

Normal tractor conformal bundles and codimension two spacelike submanifolds in Lorentzian manifolds

For every codimension two spacelike submanifold of a Lorentz manifold and each choice of a normal lightlike vector field, we introduce a canonical way to construct a tractor conformal bundle. We characterize when the induced connection of a such submanifold defines a tractor connection and then, in this case, when this tractor conformal bundle with the induced connection is standard for the induced metric. Finally, the normality condition for this tractor conformal bundle endowed with the induced connection is characterized in terms of a strong relationship between the intrinsic and the extrin…

广义Robertson-Walker时空中类光超曲面内的余维二类空子流形

Codimension two spacelike submanifolds into null hypersurfaces of generalized Robertson-Walker spacetimes

本文研究广义Robertson-Walker时空中类光锥内的余维二类空子流形，给出径向坐标条件使其分别共形微分同胚于双曲空间、圆圆柱面或球面，并得到弱俘获子流形的非存在性结果。

Complete real Kahler submanifolds in codimension two

Minimal isometric immersions F in codimension two from a complete Kahler manifold into Euclidean space had been classified for dimension greater than or equal to 3. In this note we describe the non--minimal situation by showing that, if F is real analytic but not everywhere minimal, then F is a cylinder over a real Kahler surface G in Euclidean 6-space. In addition, G can be further described.

包含在类光超柱面 $\mathcal{LC}^n\times\mathbb R$ 中的余维二子流形

Codimensions-Two Submanifolds Contained in the Light-like Hypercylinder $\mathcal{LC}^n\times\mathbb R$

本文研究洛伦兹-闵可夫斯基空间中类光超柱面上的类空余维二子流形，通过构造全局标架场分析外蕴不变量，并给出迷向、伪脐及平坦法丛子流形的局部分类定理。

Isometric rigidity in codimension two

We show that among the Euclidean submanifolds with codimension two the ones of rank two that are parabolic but nonruled are isometrically rigid. This generalizes the result in [10] that these submanifolds are genuinely rigid. In addition, we give a parametric classifications of all parabolic submanifolds.

高余维子流形的全息术：黎曼与共形情形

Holography of Higher Codimension Submanifolds: Riemannian and Conformal

本文将全息方法推广到高余维子流形，构造黎曼与共形嵌入的高阶局部不变量，发现阻碍单位定义映射逐阶构造的新不变量，并研究嵌入子流形的形式延拓问题。

洛伦兹-闵可夫斯基时空中包含于光锥的、具有平行平均曲率向量场的余维二类空子流形

Spacelike Submanifolds of Codimension Two with Parallel Mean Curvature Vector Field in Lorentz-Minkowski Spacetime Contained in the Light Cone

该研究针对洛伦兹-闵可夫斯基时空中余维二、具平行平均曲率向量场的紧致类空子流形建立积分不等式，推导出刚性结论，完整刻画了光锥内这类子流形必为类空超平面中的全脐球面。

余维数2极小子流形的能量与指标的第二内变分

Second Inner Variations of Energy and Index of Codimension $2$ Minimal Submanifolds

该研究计算了Abelian Yang–Mills–Higgs与Ginzburg–Landau能量的第二内变分，借助能量测度收敛性与应力-能量张量，用临界点指标给出了收敛到的余维数2极小子流形的Morse指标界。

Wintgen ideal submanifolds of codimension two, complex curves, and Moebius geometry

Wintgen ideal submanifolds in space forms are those ones attaining equality pointwise in the so-called DDVV inequality which relates the scalar curvature, the mean curvature and the scalar normal curvature. Using the framework of Moebius geometry, we show that in the codimension two case, the mean curvature sphere of the Wintgen ideal submanifold corresponds to an 1-isotropic holomorphic curve in a complex quadric Q. Conversely, any 1-isotropic complex curve in Q describes a 2-parameter family of m-dimensional spheres whose envelope is always a m-dimensional Wintgen ideal submanifold at the re…

Mean curvature flow of higher codimension in Riemannian manifolds

We investigate the convergence of the mean curvature flow of arbitrary codimension in Riemannian manifolds with bounded geometry. We prove that if the initial submanifold satisfies a pinching condition, then along the mean curvature flow the submanifold contracts smoothly to a round point in finite time. As a consequence we obtain a differentiable sphere theorem for submanifolds in a Riemannian manifold.

Mean curvature flow of arbitrary codimension in complex projective spaces

In this paper, we investigate the mean curvature flow of submanifolds of arbitrary codimension in $\mathbb{C}\mathbb{P}^m$. We prove that if the initial submanifold satisfies a pinching condition, then the mean curvature flow converges to a round point in finite time, or converges to a totally geodesic submanifold as $t \rightarrow \infty$. Consequently, we obtain a new differentiable sphere theorem for submanifolds in $\mathbb{C}\mathbb{P}^m$. Our work improves the convergence theorem for mean curvature flow due to Pipoli and Sinestrari {\cite{PiSi2015}}.

Equiaffine Darboux Frames for Codimension 2 Submanifolds contained in Hypersurfaces

Consider a codimension $1$ submanifold $N^n\subset M^{n+1}$, where $M^{n+1}\subset\mathbb{R}^{n+2}$ is a hypersurface. The envelope of tangent spaces of $M$ along $N$ generalizes the concept of tangent developable surface of a surface along a curve. In this paper, we study the singularities of these envelopes. There are some important examples of submanifolds that admit a vector field tangent to $M$ and transversal to $N$ whose derivative in any direction of $N$ is contained in $N$. When this is the case, one can construct transversal plane bundles and affine metrics on $N$ with the desirable …

Real Kaehler submanifolds in codimension up to four

Let $f\colon M^{2n}\to\mathbb{R}^{2n+4}$ be an isometric immersion of a Kaehler manifold of complex dimension $n\geq 5$ into Euclidean space with complex rank at least $5$ everywhere. Our main result is that, along each connected component of an open dense subset of $M^{2n}$, either $f$ is holomorphic in $\mathbb{R}^{2n+4}\cong\mathbb{C}^{n+2}$ or it is in a unique way a composition $f=F\circ h$ of isometric immersions. In the latter case, we have that $h\colon M^{2n}\to N^{2n+2}$ is holomorphic and $F\colon N^{2n+2}\to\mathbb{R}^{2n+4}$ belongs to the class, by now quite well understood, of n…

The mean curvature flow of submanifolds of high codimension

The study of the mean curvature flow from the perspective of partial differential equations began with Gerhard Huisken's pioneering work in 1984. Since that time, the mean curvature flow of hypersurfaces has been a lively area of study. Although Huisken's seminal paper is now just over twenty-five years old, the study of the mean curvature flow of submanifolds of higher codimension has only recently started to receive attention. The mean curvature flow of submanifolds is the main object of investigation in this thesis, and indeed, the central results we obtain can be considered as high codimen…

Stable submanifolds in the product of projective spaces

We provide a classification theorem for compact stable minimal immersions (CSMI) of codimension $1$ or dimension $1$ (codimension $1$ and $2$ or dimension $1$ and $2$) in the product of a complex (quaternionic) projective space with any other Riemannian manifold. We characterize the complex minimal immersions of codimension $2$ or dimension $2$ as the only CSMI in the product of two complex projective spaces. As an application, we characterize the CSMI of codimension $1$ or dimension $1$ (codimension $1$ and $2$ or dimension $1$ and $2$) in the product of a complex (quaternionic) projective sp…

A partial classification of type I singularities of the mean curvature flow in high codimension

The purpose of this article is to examine the possible shapes of type I singularities that form in the mean curvature flow of submanifolds of arbitrary codimension, assuming that the initial submanifold satisfies a particular curvature pinching condition.

Half-Lightlike Submanifold of a Lorentzian Manifolds with a conformal co-screen distribution

In this paper, we give the Cartan's formula for half-lightlike submanifolds of Lorentzian manifolds and use it to show that a screen homothetic half-lightlike submanifolds of a Lorentzian space form, with a conformal co-screen distribution are locally a lightlike triple product manifolds. Then we give a classification theorem for half-lightlike submanifolds of Lorentzian space form with constant screen principal curvatures. These results extend some results obtained in the case of lightlike hypersurfaces of Lorentzian manifolds ([1]).

Classification of codimension two deformations of rank two Riemannian manifolds

The purpose of this work is to close the local deformation problem of rank two Euclidean submanifolds in codimension two by describing their moduli space of deformations. In the process, we provide an explicit simple representation of these submanifolds, a result of independent interest by its applications. We also determine which deformations are genuine and honest, allowing us to find the first known examples of honestly locally deformable rank two submanifolds in codimension two. In addition, we study which of these submanifolds admit isometric immersions as Euclidean hypersurfaces, a prope…

An Optimal Convergence Theorem for Mean Curvature Flow of Arbitrary Codimension in Hyperbolic Spaces

In this paper, we prove that if the initial submanifold $M_0$ of dimension $n(\ge6)$ satisfies an optimal pinching condition, then the mean curvature flow of arbitrary codimension in hyperbolic spaces converges to a round point in finite time. In particular, we obtain the optimal differentiable sphere theorem for submanifolds in hyperbolic spaces. It should be emphasized that our pinching condition implies that the Ricci curvature of the initial submanifold is positive, but does not imply positivity of the sectional curvature of $M_0$.

洛伦兹流形中的余维二类空子流形与共形结构

Codimension two spacelike submanifolds in Lorentzian manifolds and conformal structures

本文提出通过黎曼共形结构和单参数自伴张量场族构造洛伦兹流形，使共形类中的度量对应余维二类空子流形的诱导度量，并建立其类光法向量场的 Weingarten 自同态与 Möbius 结构之间的双向对应关系，进而用外蕴几何刻画平坦 Möbius 结构。

Rigidity results for complete spacelike submanifolds in plane fronted waves

New rigidity results for complete non-compact spacelike submanifolds of arbitrary codimension in plane fronted waves are obtained. Under appropriate assumptions, we prove that a complete spacelike submanifold in these spacetimes is contained in a characteristic lightlike hypersurface. Moreover, for a complete codimension two extremal submanifold in a plane fronted wave we show sufficient conditions to guarantee that it is a (totally geodesic) wavefront.

Mean Curvature Flow of Higher Codimension in Hyperbolic Spaces

In this paper we investigate the convergence for the mean curvature flow of closed submanifolds with arbitrary codimension in space forms. Particularly, we prove that the mean curvature flow deforms a closed submanifold satisfying a pinching condition in a hyperbolic space form to a round point in finite time.

球面中余维数高的闭极小子流形的 pinch 常数

The pinching constant for closed minimal submanifolds of high codimension in the sphere

本文针对单位球面中余维数 $q\geqslant 2$ 的闭极小子流形，推导了非全测地情形下其第二基本形式平方长度最大值的下界估计。

Isoperimetric Inequalities for Minimal Submanifolds in Riemannian Manifolds: A Counterexample in Higher Codimension

For compact Riemannian manifolds with convex boundary, B.White proved the following alternative: Either there is an isoperimetric inequality for minimal hypersurfaces or there exists a closed minimal hypersurface, possibly with a small singular set. There is the natural question if a similar result is true for submanifolds of higher codimension. Specifically, B.White asked if the non-existence of an isoperimetric inequality for k-varifolds implies the existence of a nonzero, stationary, integral k-varifold. We present examples showing that this is not true in codimension greater than two. The …

实Kaehler子流形的第二基本形式

The second fundamental form of the real Kaehler submanifolds

本文证明了实Kaehler子流形的第二基本形式在Yan-Zheng猜想成立时的逐点预期行为，为低余维非全纯Kaehler子流形的分类提供了基础，并通过反例验证了余维数上界设定的合理性。

A normal form for a real 2-codimensional submanifold in $\mathbb{C}^{N+1}$ near a CR singularity

We construct a formal normal form for a real 2-codimensional submanifold $M\subset\mathbb{C}^{N+1}$ near a CR singularity approximating the sphere. This result gives a higher dimensional extension of Huang-Yin's normal form in $\mathbb{C}^{2}$.

Solitons for the inverse mean curvature flow

We investigate self-similar solutions to the inverse mean curvature flow in Euclidean space. In the case of one dimensional planar solitons, we explicitly classify all homothetic solitons and translators. Generalizing Andrews' theorem that circles are the only compact homothetic planar solitons, we apply the Hsiung-Minkowski integral formula to prove the rigidity of the hypersphere in the class of compact expanders of codimension one. We also establish that the moduli space of compact expanding surfaces of codimension two is big. Finally, we update the list of Huisken-Ilmanen's rotational expa…

欧几里得空间中的非全纯Kaehler子流形

Non-holomorphic Kaehler submanifolds of Euclidean space

本文研究了Kaehler流形到欧几里得空间的低余维非全纯等距浸入，证实了Yan-Zheng猜想至余维p=6，并在附加假设下将结论推广至余维7≤p≤11。

Classification results for biharmonic submanifolds in spheres

We classify biharmonic submanifolds with certain geometric properties in Euclidean spheres. For codimension 1, we determine the biharmonic hypersurfaces with at most two distinct principal curvatures and the conformally flat biharmonic hypersurfaces. We obtain some rigidity results for pseudo-umbilical biharmonic submanifolds of codimension 2 and for biharmonic surfaces with parallel mean curvature vector field. We also study the type, in the sense of B-Y. Chen, of compact proper biharmonic submanifolds with constant mean curvature in spheres.

Submanifolds with nonpositive extrinsic curvature

We prove that complete submanifolds, on which the Omori-Yau weak maximum principle for the Hessian holds, with low codimension and bounded by cylinders of small radius must have points rich in large positive extrinsic curvature. The lower the codimension is, the richer such points are. The smaller the radius is, the larger such curvatures are. This work unifies and generalizes several previous results on submanifolds with nonpositive extrinsic curvature.

Characterization on projective submanifolds of codimensions 2 and 3

In this article we give a necessary and sufficient condition to characterize projective submanifolds in ${\mathbb P}^N$ with codimensions 2 and 3. The conditions involve the Chern classes of the manifold and a very ample line bundle on the manifold. This generalizes our earlier characterization for hypersurfaces. The higher codimensional cases are proposed as a general question.

Conformal Kaehler Euclidean submanifolds

Let $f\colon M^{2n}\to\mathbb{R}^{2n+\ell}$, $n \geq 5$, denote a conformal immersion into Euclidean space with codimension $\ell$ of a Kaehler manifold of complex dimension $n$ and free of flat points. For codimensions $\ell=1,2$ we show that such a submanifold can always be locally obtained in a rather simple way, namely, from an isometric immersion of the Kaehler manifold $M^{2n}$ into either $\mathbb{R}^{2n+1}$ or $\mathbb{R}^{2n+2}$, the latter being a class of submanifolds already extensively studied.

Mean Curvature Flow of Compact Spacelike Submanifolds in Higher Codimension

We prove long-time existence for mean curvature flow of a smooth $n$-dimensional spacelike submanifold of an $n+m$ dimensional manifold whose metric satisfies the timelike curvature condition.

单纯体积与余维数为一的孤立、闭全测地子流形

Simplicial volume and isolated, closed totally geodesic submanifolds of codimension one

本文证明含余维数一孤立闭全测地子流形的非正曲率闭流形具有正单纯体积，并推出非正弯曲解析流形在万有覆叠含余维数一平坦时的二分结论。

The isoperimetric inequality for a minimal submanifold in Euclidean space

We prove a Sobolev inequality which holds on submanifolds in Euclidean space of arbitrary dimension and codimension. This inequality is sharp if the codimension is at most 2. As a special case, we obtain a sharp isoperimetric inequality for minimal submanifolds in Euclidean space of codimension at most 2.

具有脐性类光法向截面的余维二类空子流形及其与类光超曲面的关系

Codimension-Two Spacelike Submanifolds with Umbilical Lightlike Normal Sections and Their Relationship to Lightlike Hypersurfaces

本文研究洛伦兹时空中具有脐性类光法向方向的余维二类空子流形，证明其受强几何拓扑约束，并建立分解定理：此类子流形可嵌入类光超曲面，且在全脐性条件下与共形平坦时空相关，为视界研究提供几何框架。

A Dajczer-Rodriguez Type Cylinder Theorem for Real Kahler Submanifolds

In 1991, Dajczer and Rodriguez proved in [10] that a complete minimal real Kahler submanifold of codimension 2, if with complex dimension > 2, would be either holomorphic, or a cylinder, or complex ruled. In this article, we generalize their result to real analytic complete real Kahler submanifolds of codimension 4. The conclusion is that such the submanifold, if with complex dimension > 4, would be either partially holomorphic, or a cylinder, or a twisted cylinder in the sense that the complex relative nullity foliation is contained in a strictly larger holomorphic foliation, whose leaves are…

Minkowski formulae and Alexandrov theorems in spacetime

The classical Minkowski formula is extended to spacelike codimension-two submanifolds in spacetimes which admit "hidden symmetry" from conformal Killing-Yano two-forms. As an application, we obtain an Alexandrov type theorem for spacelike codimension-two submanifolds in a static spherically symmetric spacetime: a codimension-two submanifold with constant normalized null expansion (null mean curvature) must lie in a shear-free (umbilical) null hypersurface. These results are generalized for higher order curvature invariants. In particular, the notion of mixed higher order mean curvature is intr…

Codimension two marginally trapped submanifolds in Robertson-Walker spaces

We give a local characterization of codimension two submanifolds which are marginally trapped in Robertson-Walker spaces, in terms of an algebraic equation to be satisfied by the height function. We prove the existence of a large number of local solutions. We refine the description in the case of curves with null acceleration in three-dimensional spaces Robertson-Walker spaces, and in the case of codimension two submanifolds whose second fundamental form is null

The Gauss image of entire graphs of higher codimension and Bernstein type theorems

Under suitable conditions on the range of the Gauss map of a complete submanifold of Euclidean space with parallel mean curvature, we construct a strongly subharmonic function and derive a-priori estimates for the harmonic Gauss map. The required conditions here are more general than in previous work and they therefore enable us to improve substantially previous results for the Lawson-Osseman problem concerning the regularity of minimal submanifolds in higher codimension and to derive Bernstein type results.

Kaehler submanifolds of hyperbolic space

We present several local and global results on isometric immersions of Kaehler manifolds $M^{2n}$ into hyperbolic space $\Hy^{2n+p}$. For instance, a classification is given in the case of dimension $n\geq 4$ and codimension $p=2$. Moreover, as corollaries of general results, we conclude that there are no isometric immersion in codimension $p\leq n-2$ if the Kaehler manifold is of dimension $n\geq 4$ and either has a point of positive holomorphic sectional curvature or is compact.

Nonnegatively curved Euclidean submanifolds in codimension two

We provide a classification of compact Euclidean submanifolds $M^n\subset{\mathbb{R}}^{n+2}$ with nonnegative sectional curvature, for $n\ge 3$. The classification is in terms of the induced metric (including the diffeomorphism classification of the manifold), and we study the structure of the immersions as well. In particular, we provide the first known example of a nonorientable quotient $({\mathbb{S}}^{n-1}\times{\mathbb{S}}^1)/{\mathbb{Z}_2}\subset{\mathbb{R}}^{n+2}$ with nonnegative curvature. For the 3-dimensional case, we show that either the universal cover is isometric to ${\mathbb{S}…

复射影空间中高余维平均曲率流

High Codimension Mean Curvature Flow in the Complex Projective Space

本文研究复射影空间中高余维紧致子流形的平均曲率流，在二次夹紧条件下建立余维估计，证明奇异时刻重缩放收敛到光滑余维一极限流，并推广了Pipoli和Sinestrari的工作。

Frame bundle approach to generalized minimal submanifolds

We extend the notion of $r$-minimality of a submanifold in arbitrary codimension to $u$-minimality for a multi-index $u\in\mathbb{N}^q$, where $q$ is the codimension. This approach is based on the analysis on the frame bundle of orthonormal frames of the normal bundle to a submanifold and vector bundles associated with this bundle. The notion of $u$-minimality comes from the variation of $σ_u$-symmetric function obtained from the family of shape operators corresponding to all possible bases of the normal bundle. We obtain the variation field, which gives alternative definition of $u$--minimali…

Codimension reduction in symmetric spaces

In this paper we give a short geometric proof of a generalization of a well-known result about reduction of codimension for submanifolds of Riemannian symmetric spaces.

New Developments in Mean Curvature Flow of Arbitrary Codimension Inspired By Yau Rigidity Theory

In this survey, we will focus on the mean curvature flow theory with sphere theorems, and discuss the recent developments on the convergence theorems for the mean curvature flow of arbitrary codimension inspired by the Yau rigidity theory of submanifolds. Several new differentiable sphere theorems for submanifolds are obtained as consequences of the convergence theorems for the mean curvature flow. It should be emphasized that Theorem 4.1 is an optimal convergence theorem for the mean curvature flow of arbitrary codimension, which implies the first optimal differentiable sphere theorem for sub…