子流形的具有位置向量方向外力场的平均曲率流

考虑欧氏空间R~(n+p)中n(≥2)维闭子流形沿平均曲率向量场加上一个位置向量方向外力场的流的发展.设子流形任意一点处平均曲率向量非零和第二基本形式的模长以平均曲率向量长度的常数倍(仅与n有关)为界,我们证明了若外力场很小时,拼挤子流形要么在有限时间内收缩为一点,要么子流形在任意时刻都存在;若外力场足够大时,子流形发散到无穷大;同时,当流发展到极限位置时,规范化子流形都光滑收敛到R~(n+p)中的一个n+1维子空间中的标准球面.     

欧氏空间中子流形的曲率与几何性质

研究了欧氏空间En p中具常数量曲率n(n-1)r的n(n>2)维完备连通子流形,得到了En p截面曲率非负且法联络平坦的完备连通子流形的一个分类定理.     

常曲率空间中具正Ricci曲率的子流形

设S~(n+p)(1)是一单位球面,M~n是浸入S~(n+p)(1)的具有非零平行平均曲率向量的n维紧致子流形.证明了当n≥4,p≥2时,如果M~n的Ricci曲率不小于(n-2)(1+H~2),则M~n是全脐的或者M~n的Ricci曲率等于(n-2)(1+H~2),进而M~n的几何分类被完全给出.     

单位球面中具平行单位平均曲率向量的子流形

设M是n-维闭黎曼流形,等距浸入(n+p)-维单位球空间S^n+p,具有平行的单位平均曲率向量。若S≤min{2n/3,2(n-1)^1/2},其中S是M的第二基本形式长度的平方,则M是S^n+p的一个(n+1)-维全测地子流形Sⁿ⁺¹中的超曲面。     

关于共形平坦流形中子流形的不等式

本文目的在于建立共形平坦黎曼流形中子流形的数量曲率截面曲率间关系的几个不等式,在流形是常曲率的情况下,这些不等式改进了B.Y.Chen和M.Okumura的结果。§1.基本公式和引理设M~(n+p)是一个n+p维的共形平坦黎曼流形,V~n是M~(n+p)的n维子流形。在M~(n+p)中选取局     

关于伪脐子流形的一个整体定理

设 M~n 是截面曲率为 c 的(n+p)维黎曼空间 M~(n+p)(c)中 n 维子流形。如在 M~n 上存在函数λ使得:〈h(x,y),H〉=λ〈x,y〉成立,其中λ=H~2,则称 M~n是 M~(n+p)(c)的伪脐子流形。本文得到常曲率空间中紧致伪脐子流形的一个整体定理(定理2.1)。     

双曲空间Hn+p(-1)中具常数量曲率的完备子流形

设Mn是Hn p(-1)中具有常标准数量曲率的n维完备子流形,本文证明了这种完备子流形的某些内蕴刚性定理和分类定理,并对超曲面的情形进行了研究．     

关于S~(n p)(1)的紧致子流形的第一特征值(英文)

记H0 =maxx∈M｜H(x) ｜ ,其中H(x)为Sn p( 1 )的n维紧致子流形的平均曲率向量 .则其Lplace算子的第一特征值满足 :λ1≤n nH20 .     

欧氏空间中紧致子流形的积分公式(英文)

本文研究了(n+p)维欧氏空间R~(n+p)中n维定向紧致无边子流形Mn的积分公式的问题.首先定义了M~n沿其单位平均曲率向量场ξ方向的高阶平均曲率H~r(0≤r≤n);然后,利用活动标架与外微分法,获得了关于Mn的一个新的积分公式.新公式推广了余维数p=1即超曲面情况下的经典积分公式.     

常曲率空间中平均曲率为常数的迷向子流形

设M~n是n维黎曼流形,S~(n+p)(e)是n+p维截面曲率为常数c的黎曼流形,设fM~n→S~(n+p)(c)是等距浸入,我们分别用和表示f(M~n)和S~(n+p)(c)的协变微分,那么浸入f的第二基本形式A为 A(X,Y)=x~Y-x~Y     

RECENT PROGRESS ON SPHERICAL HARMONIC APPROXIMATION MADE BY BNU RESEARCH GROUP ——In memory of Professor Sun Yongsheng

As early as in 1990, Professor Sun Yongsheng, suggested his students at Beijing Normal University to consider research problems on the unit sphere. Under his guidance and encouragement his students started the research on spherical harmonic analysis and approximation. In this paper, we incompletely introduce the main achievements in this area obtained by our group and relative researchers during recent 5 years （2001-2005）. The main topics are： convergence of Cesaro summability, a.e. and strong summability of Fourier-Laplace series; smoothness and K-functionals; Kolmogorov and linear widths.     

A unified approach to certain problems of best local approximation

In this paper we study best local quasi-rational approximation and best local approximation from finite dimensional subspaces of vectorial functions of several variables. Our approach extends and unifies several problems concerning best local multi-point approximation in different norms.     

Boundedness for commutators of multipliers on Hardy type spaces

In this paper, we study the commutators generalized by multipliers and a BMO function. Under some assumptions, we establish its boundedness properties from certain atomic Hardy space Hb^p（R^n） into the Lebesgue space L^p with p 〈 1.     

THE 8~(th) INTERNATIONAL CONGRESS ON INDUSTRIAL AND APPLIED MATHEMATICS

<正>August 10-14,2015Beijing,ChinaThe International Congress on Industrial and Applied Mathematics(ICIAM)is the premier international congress in the field of applied mathematics held every four years under the auspices of the International Council for Industrial and Applied Mathematics.From August 10 to 14,2015,mathematicians,scientists     

Towards Excellence in Science Chinese Academy of Sciences

<正>May 26,2014,Beijing Science is a human enterprise in the pursuit of knowledge.The scientific revolution that occurred in the 17th Century initiated the advances of modern science.The scientific knowledge system created by     

Bounds for the zeros of polynomials

Let P(z)=∑↓j=0↑n ajx^j be a polynomial of degree n. In this paper we prove a more general result which interalia improves upon the bounds of a class of polynomials. We also prove a result which includes some extensions and generalizations of Enestrǒm-Kakeya theorem.     

Boundedness of commutators related to Marcinkiewicz integrals on hardy type spaces

In this paper, the authors study the boundedness of the operator [μΩ, b], the commutator generated by a function b ∈ Lipβ(Rn)(0 ＜β≤ 1) and the Marcinkiewicz integrals μΩ, on the classical Hardy spaces and the Herz-type Hardy spaces in the case Ω∈ Lipα(Sn-1)(0 ＜α≤ 1).     

Jacobi polynomials used to invert the laplace transform

Given the Laplace transform F(s) of a function f(t), we develop a new algorithm to find an approximation to f(t) by the use of the classical Jacobi polynomials. The main contribution of our work is the development of a new and very effective method to determine the coefficients in the finite series expansion that approximation f(t) in terms of Jacobi polynomials. Some numerical examples are illustrated.     

Generalization of the interaction between Haar approximation and polynomial operators to higher order methods

In applications it is useful to compute the local average empirical statistics on u. A very simple relation exists when of a function f（u） of an input u from the local averages are given by a Haar approximation. The question is to know if it holds for higher order approximation methods. To do so, it is necessary to use approximate product operators defined over linear approximation spaces. These products are characterized by a Strang and Fix like condition. An explicit construction of these product operators is exhibited for piecewise polynomial functions, using Hermite interpolation. The averaging relation which holds for the Haar approximation is then recovered when the product is defined by a two point Hermite interpolation.