arXiv subjects

Bang-Yen Chen

Publications and source records attributed to Bang-Yen Chen.

70 records · Page 4Linked to original sources

arXiv2013

Two optimal inequalities for anti-holomorphic submanifolds and their applications

The CR $δ$-invariant for CR-submanifolds was introduced in a recent article [B. Y. Chen, An optimal inequality for CR-warped products in complex space forms involving CR $δ$-invariant, Internat. J. Math. 23} (2012), no. 3, 1250045 (17 pages)]. In this paper, we prove two new optimal inequalities for anti-holomorphic submanifolds in complex space forms involving the CR $δ$-invariant. Moreover, we obtain some classification results for certain anti-holomorphic submanifolds in complex space forms which satisfy the equality case of either inequality.

math.DG↗

arXiv2013

The 2-ranks of connected compact Lie groups

The 2-rank of a compact Lie group $G$ is the maximal possible rank of the elementary 2-subgroup ${\mathbb Z}_{2}\times... {\mathbb Z}_{2}$ of $G$. The study of 2-ranks (and $p$-rank for any prime $p$) of compact Lie groups was initiated in 1953 by A. Borel and J.-P. Serre. Since then the 2-ranks of compact Lie groups have been investigated by many mathematician. The 2-ranks of compact Lie groups relate closely with several important areas in mathematics. In this article, we survey important results concerning 2-ranks of compact Lie groups. In particular, we present the complete determination of 2-ranks of compact connected simple Lie groups $G$ via the 2-numbers introduced by B. Y. Chen and T. Nagano in [Un invariant gémétrique riemannien, C. R. Acad. Sci. Paris, 295 (1982), 389--391] and [A Riemannian geometric invariant and its applications to a problem of Borel and Serre, Trans. Amer. Math. Soc. 308 (1988), 273--297].

math.GR↗

arXiv2013

On Wintgen ideal surfaces

Wintgen proved in [P. Wintgen, Sur l'inégalité de Chen-Willmore, C. R. Acad. Sci. Paris, 288 (1979), 993--995] that the Gauss curvature $K$ and the normal curvature $K^D$ of a surface in the Euclidean 4-space $E^4$ satisfy $$K+|K^D|\leq H^2,$$ where $H^2$ is the squared mean curvature. A surface $M$ in $\E4$ is called a {Wintgen ideal} surface if it satisfies the equality case of the inequality identically. Wintgen ideal surfaces in $E^4$ form an important family of surfaces; namely, surfaces with circular ellipse of curvature. In this paper, we provide a brief survey on some old and recent results on Wintgen ideal surfaces and more generally Wintgen ideal submanifolds in definite and indefinite real space forms.

math.DG↗

arXiv2013

$δ$-invariants for Lagrangian submanifolds of complex space forms

The famous Nash embedding theorem published in 1956 was aiming for the opportunity to use extrinsic help in the study of (intrinsic) Riemannian geometry, if Riemannian manifolds could be regarded as Riemannian submanifolds. However, this hope had not been materialized yet according to \cite{G}. The main reason for this was the lack of control of the extrinsic properties of the submanifolds by the known intrinsic invariants. In order to overcome such difficulties as well as to provide answers to an open question on minimal immersions, the first author introduced in the early 1990's new types of Riemannian invariants, his so-called $δ$-curvatures, different in nature from the "classical" Ricci and scalar curvatures. The purpose of this article is to present some old and recent results concerning $δ$-invariants for Lagrangian submanifolds of complex space forms.

math.DG↗

arXiv2013

On purely real surfaces in Kaehler surfaces and Lorentz surfaces in Lorentzian Kaehler surfaces

An immersion $ϕ\colon M \to \tilde M$ of a manifold $M$ into an indefinite Kaehler manifold $\tilde M$ is called purely real if the almost complex structure $J$ on $\tilde M$ carries the tangent bundle of $M$ into a transversal bundle. In this article we survey some recent results on purely real surfaces in Kaehler surfaces as well as on Lorentz surfaces in Lorentzian Kaehler surfaces.

math.DG↗

arXiv2013

Riemannian Submanifolds: A Survey

Submanifold theory is a very active vast research field which plays an important role in the development of modern differential geometry. This branch of differential geometry is still so far from being exhausted; only a small portion of an exceedingly fruitful field has been cultivated, much more remains to be discovered. In this article, the author provides a broad review of Riemannian submanifolds in differential geometry.

math.DG↗

arXiv2013

Submanifolds of warped product manifolds $I\times_f S^{m-1}(k)$}} from a $p$-harmonic viewpoint

We study $p$-harmonic maps, $p$-harmonic morphisms, biharmonic maps, and quasiregular mappings into submanifolds of warped product Riemannian manifolds ${I}\times_f S^{m-1}(k)\, $ of an open interval and a complete simply-connecteded $(m-1)$-dimensional Riemannian manifold of constant sectional curvature $k$. We establish an existence theorem for $p$-harmonic maps and give a classification of complete stable minimal surfaces in certain three dimensional warped product Riemannian manifolds ${\bf R}\times_f S^{2}(k)\, ,$ building on our previous work. When $f \equiv\, $ Const. and $k=0$, we recapture a generalized Bernstein Theorem and hence the Classical Bernstein Theorem in $R^3$. We then extend the classification to parabolic stable minimal hypersurfaces in higher dimensions.

math.AP↗

arXiv2013

$δ$-Invariants, Inequalities of Submanifolds and Their Applications

The famous Nash embedding theorem was aimed for in the hope that if Riemannian manifolds could be regarded as Riemannian submanifolds, this would then yield the opportunity to use extrinsic help. However, as late as 1985 (see \cite{G}) this hope had not been materialized. The main reason for this is due to the lack of controls of the extrinsic properties of the submanifolds by the known intrinsic invariants. In order to overcome such difficulties as well as to provide answers to an open question on minimal immersions, we introduced in the early 1990's new types of Riemannian invariants, known as the $δ$-invariants or the so-called Chen invariants, different in nature from the "classical" Ricci and scalar curvatures. At the same time we also able to establish general optimal relations between the new intrinsic invariants and the main extrinsic invariants for Riemannian submanifolds. Since then many results concerning these invariants, inequalities, related subjects, and their applications have been obtained by many geometers. The main purpose of this article is thus to provide an extensive and comprehensive survey of results over this very active field of research done during the last fifteen years. Several related inequalities and their applications are presented in this survey article as well.

math.DG↗

arXiv2013

Solutions to homogeneous Monge-Ampère equations of homothetic functions and their applications to production models in economics

Mathematically, a homothetic function is a function of the form $f({\bf x})=F(h(x_1,...,x_n))$, where $h$ is a homogeneous function of any degree $d\ne 0$ and $F$ is a monotonically increasing function. In economics homothetic functions are production functions whose marginal technical rate of substitution is homogeneous of degree zero. In this paper we classify homothetic functions satisfying the homogeneous Monge-Ampère equation. Several applications to production models in economics will also be given.

math.AP↗

arXiv2013

Laplace Transformations of Submanifolds

Let $x : M \to E^m$ be an isometric immersion of a Riemannian manifold $M$ into a Euclidean $m$-space. Denote by $Δ$ the Laplace operator of $M$. Then $Δ$ gives rise to a differentiable map $L :M \to E^m$, called the Laplace map, defined by $L(p)=(Δx)(p)$, $p\in M$. We call $L(M)$ the Laplace image, and the transformation $L :M \to L(M)$ from $M$ onto its Laplace image $L(M)$ the {\it Laplace transformation}. In this monograph, we provide a fundamental study of the Laplace transformations of Euclidean submanifolds.

math.DG↗

arXiv2013

Curvature inequalities for Lagrangian submanifolds: the final solution

Let $M$ be an $n$-dimensional Lagrangian submanifold of a complex space form. We prove a pointwise inequality $$δ(n_1,\ldots,n_k) \leq a(n,k,n_1,\ldots,n_k) \|H\|^2 + b(n,k,n_1,\ldots,n_k)c,$$ with on the left hand side any delta-invariant of the Riemannian manifold $M$ and on the right hand side a linear combination of the squared mean curvature of the immersion and the constant holomorphic sectional curvature of the ambient space. The coefficients on the right hand side are optimal in the sence that there exist non-minimal examples satisfying equality at at least one point. We also characterize those Lagrangian submanifolds satisfying equality at any of their points. Our results correct and extend those given in [B.-Y. Chen and F. Dillen, Optimal general inequalities for Lagrangian submanifolds in complex space forms, J. Math. Anal. Appl. 379 (2011), 229--239].

math.DG↗

arXiv2013

A tour through $δ$-invariants: From Nash's embedding theorem to ideal immersions, best ways of living and beyond

First I will explain my motivation to introduce the $δ$-invariants for Riemannian manifolds. I will also recall the notions of ideal immersions and best ways of living. Then I will present a few of the many applications of $δ$-invariants to several areas in mathematics. Finally, I will present two optimal inequalities involving $δ$-invariants for Lagrangian submanifolds obtained very recently in joint papers with F. Dillen, J. Van der Veken and L. Vrancken.

math.DG↗

arXiv2013

Submanifolds with parallel mean curvature vector in Riemannian and indefinite space forms

A submanifold of a pseudo-Riemannian manifold is said to have parallel mean curvature vector if the mean curvature vector field H is parallel as a section of the normal bundle. Submanifolds with parallel mean curvature vector are important since they are critical points of some natural functionals. In this paper, we survey some classical and recent results on submanifolds with parallel mean curvature vector. Special attention is paid to the classification of space-like and Lorentz surfaces with parallel mean curvature vector in Riemannian and indefinite space forms.

math.DG↗

arXiv2013

Segre embedding and related maps and immersions in differential geometry

Segre embedding was introduced by C. Segre (1863--1924) in his famous 1891 article \cite{segre}. The Segre embedding plays an important roles in algebraic geometry as well as in differential geometry, mathematical physics, and coding theory. In this article, we survey main results on Segre embedding in differential geometry. Moreover, we also present recent differential geometric results on maps and immersions which are constructed in ways similar to Segre embedding.

math.AG↗

arXiv2013

A survey on geometry of warped product submanifolds

The warped product $N_1\times_f N_2$ of two Riemannian manifolds $(N_1,g_1)$ and $(N_2,g_2)$ is the product manifold $N_1\times N_2$ equipped with the warped product metric $g=g_1+f^2 g_2$, where $f$ is a positive function on $N_1$. The notion of warped product manifolds is one of the most fruitful generalizations of Riemannian products. Such notion plays very important roles in differential geometry as well as in physics, especially in general relativity. Warped product manifolds have been studied for a long period of time. In contrast, the study of warped product submanifolds was only initiated around the beginning of this century. In this article we survey important results on warped product submanifolds in various ambient manifolds. It is the author's hope that this survey article will provide a good introduction on the theory of warped product submanifolds as well as a useful reference for further research on this vibrant research subject.

math.DG↗

arXiv2011

Geometry of PR-warped products in para-Kaehler manifolds

In this paper, we initiate the study of $\p R$-warped products in para-Kähler manifolds and prove some fundamental results on such submanifolds. In particular, we establish a general optimal inequality for $\p R$-warped products in para-Kähler manifolds involving only the warping function and the second fundamental form. Moreover, we completely classify $\p R$-warped products in the flat para-Kähler manifold with least codimension which satisfy the equality case of the inequality.

math.DG↗