In this paper,we study the complete space-like submanifold Mn with constant scalar curvature R≤c in the de Sitter space Spn+p(c) and obtain a pinching condition for Mn to be totally umbilical ones.The result generali...In this paper,we study the complete space-like submanifold Mn with constant scalar curvature R≤c in the de Sitter space Spn+p(c) and obtain a pinching condition for Mn to be totally umbilical ones.The result generalizes that in [5,Main Theorem] to higher codimension and give a complement for n=2 there.展开更多
Goldberg and Wu studied a conformally flat manifold M with constant scalar curvature. When the Ricci curvature of M is of bounded below or positive,the conditions of M becoming a constant curvature manifold are obtain...Goldberg and Wu studied a conformally flat manifold M with constant scalar curvature. When the Ricci curvature of M is of bounded below or positive,the conditions of M becoming a constant curvature manifold are obtained. In this paper,we consider conharmonically flat manifolds and quasi conformally flat manifolds with constant saclar curvature. The corresponding results are generalized.展开更多
Let E_(s)^(m+p+1) ?R_(s+1)^(m+p+2)(m≥ 2,p≥ 1,0≤s≤p) be the standard(punched)light-cone in the Lorentzian space R_(s+1)^(m+p+2),and let Y:M^(m)→E_(s)^(m+p+1) be a space-like immersed submanifold of dimension m.The...Let E_(s)^(m+p+1) ?R_(s+1)^(m+p+2)(m≥ 2,p≥ 1,0≤s≤p) be the standard(punched)light-cone in the Lorentzian space R_(s+1)^(m+p+2),and let Y:M^(m)→E_(s)^(m+p+1) be a space-like immersed submanifold of dimension m.Then,in addition to the induced metric g on Mm,there are three other important invariants of Y:the Blaschke tensor A,the conic second fundamental form B,and the conic Mobius form C;these are naturally defined by Y and are all invariant under the group of rigid motions on E_(s)^(m+p+1).In particular,g,A,B,C form a complete invariant system for Y,as was originally shown by C.P.Wang for the case in which s=0.The submanifold Y is said to be Blaschke isoparametric if its conic Mobius form C vanishes identically and all of its Blaschke eigenvalues are constant.In this paper,we study the space-like Blaschke isoparametric submanifolds of a general codimension in the light-cone E_(s)^(m+p+1) for the extremal case in which s=p.We obtain a complete classification theorem for all the m-dimensional space-like Blaschke isoparametric submanifolds in Epm+p+1of constant scalar curvature,and of two distinct Blaschke eigenvalues.展开更多
The following article has been retracted due to the investigation of complaints received against it. Mr. Mohammadali Ghorbani (corresponding author and also the last author) cheated the authors’ name: Alireza Heidari...The following article has been retracted due to the investigation of complaints received against it. Mr. Mohammadali Ghorbani (corresponding author and also the last author) cheated the authors’ name: Alireza Heidari, Foad Khademi,Jahromi and Roozbeh Amiri. The scientific community takes a very strong view on this matter and we treat all unethical behavior such as plagiarism seriously. This paper published in Vol.3 No.4 334-339, 2012, has been removed from this site.展开更多
Let Mn be a closed submanifold isometrically immersed in a unit sphere Sn . Denote by R, H and S, the normalized +p scalar curvature, the mean curvature, and the square of the length of the second fundamental form of ...Let Mn be a closed submanifold isometrically immersed in a unit sphere Sn . Denote by R, H and S, the normalized +p scalar curvature, the mean curvature, and the square of the length of the second fundamental form of Mn, respectively. Suppose R is constant and ≥1. We study the pinching problem on S and prove a rigidity theorem for Mn immersed in Sn +pwith parallel nor- malized mean curvature vector field. When n≥8 or, n=7 and p≤2, the pinching constant is best.展开更多
Let Mn be a closed spacelike submanifold isometrically immersed in de Sitter space S^n+p _p(c).Denote by R,H and S the normalized scalar curvature,the mean curvature and the square of the length of the second fundamen...Let Mn be a closed spacelike submanifold isometrically immersed in de Sitter space S^n+p _p(c).Denote by R,H and S the normalized scalar curvature,the mean curvature and the square of the length of the second fundamental form of Mn,respectively.Suppose R is constant and R≤c. The pinching problem on S is studied and a rigidity theorem for Mn immersed in ~S^n+p _p(c) with parallel normalized mean curvature vector field is proved.When n≥3, the pinching constant is the best.Thus,the mistake of the paper “Space-like hypersurfaces in de Sitter space with constant scalar curvature”(see Manus Math,1998,95:499-505) is corrected.Moreover,the reduction of the codimension when Mn is a complete submanifold in S^n+p _p(c) with parallel normalized mean curvature vector field is investigated.展开更多
We consider a similarity kinematic of a deltoid by studying locally the scalar curvature for the corresponding two dimensional kinematic surfaces in the Euclidean space . We prove that there is no two dimensional kine...We consider a similarity kinematic of a deltoid by studying locally the scalar curvature for the corresponding two dimensional kinematic surfaces in the Euclidean space . We prove that there is no two dimensional kinematic surfaces with scalar curvature K is non-zero constant. We describe the equations that govern such the surfaces.展开更多
Under the assumption that the normalized mean curvature vector is parallel in the normal bundle, by using the generalized ChengYau's self-adjoint differential operator, here we obtain some rigidity results for compac...Under the assumption that the normalized mean curvature vector is parallel in the normal bundle, by using the generalized ChengYau's self-adjoint differential operator, here we obtain some rigidity results for compact submanifolds with constant scalar curvature and higher codimension in the space forms.展开更多
Let f: Mn(?)Sn+1 C Rn+2 be an n-dimensional complete oriented Rieman-nian manifold minimally immersed in an (n+1)-dimensional unit sphere Sn+1. Denote by S_+~n+1 the upper closed hemisphere. If f(Mn)(?)_+~n+1, then un...Let f: Mn(?)Sn+1 C Rn+2 be an n-dimensional complete oriented Rieman-nian manifold minimally immersed in an (n+1)-dimensional unit sphere Sn+1. Denote by S_+~n+1 the upper closed hemisphere. If f(Mn)(?)_+~n+1, then under some curvature conditions the authors can get that the isometric immersion is a totally embedding. They also generalize a theorem of Li Hai Zhong on hypersurface of space form with costant scalar curvature.展开更多
A Finsler metric on a manifold M with its flag curvature K is said to be almost isotropic flag curvature if K = 3c + δ where δ and c are scalar functions on M. In this paper, we establish the intrinsic relation bet...A Finsler metric on a manifold M with its flag curvature K is said to be almost isotropic flag curvature if K = 3c + δ where δ and c are scalar functions on M. In this paper, we establish the intrinsic relation between scalar functions c(x) and a(x). More general, by invoking the Ricci identities for a one form, we investigate Finsler metric of weakly isotropic flag curvature K = 3θ/F + δ and show that F has constant flag curvature if θ is horizontally parallel.展开更多
In this paper we consider the homothetic motion of Lorentzian circle by studying the scalar curvature for the corresponding cyclic surface locally. We prove that if the scalar curvature is constant, then . We describe...In this paper we consider the homothetic motion of Lorentzian circle by studying the scalar curvature for the corresponding cyclic surface locally. We prove that if the scalar curvature is constant, then . We describe the equations that govern such surfaces.展开更多
The most important Moebius invariants in the Moebius differential geometry of submanifolds in S^n+p are the Moebius metric g, the Moebius second fundamental form B, the Moebius form φ and the Blaschke tensor A. In t...The most important Moebius invariants in the Moebius differential geometry of submanifolds in S^n+p are the Moebius metric g, the Moebius second fundamental form B, the Moebius form φ and the Blaschke tensor A. In this paper, we obtain the upper bound of the Moebius scalar curvature of submanifolds with parallel Moebius form in S^n+p.展开更多
In this paper we prove an existence result for the nonlinear elliptic problem:-△u = Ku5,u 〉 0 in Ω,u = 0 on Ω,where Ω is a smooth bounded domain of R3 and K is a positive function in Ω.Our method relies on stud...In this paper we prove an existence result for the nonlinear elliptic problem:-△u = Ku5,u 〉 0 in Ω,u = 0 on Ω,where Ω is a smooth bounded domain of R3 and K is a positive function in Ω.Our method relies on studying its corresponding subcritical approximation problem and then using a topological argument.展开更多
设x:M→An+1是由定义在凸域ΩAn上的某局部严格凸函数xn+1=f(x1,...,xn)给出的超曲面.考虑Hessian度量 g =∑2fxixjdxidxj.若(M,g)是具有非负李奇曲率的紧致Hessian流形且仿射Khler-Scalar曲率为零,作者证明了如果Δρ≤nρ2...设x:M→An+1是由定义在凸域ΩAn上的某局部严格凸函数xn+1=f(x1,...,xn)给出的超曲面.考虑Hessian度量 g =∑2fxixjdxidxj.若(M,g)是具有非负李奇曲率的紧致Hessian流形且仿射Khler-Scalar曲率为零,作者证明了如果Δρ≤nρ2,则函数f一定是二次多项式,其中ρ=[det(fij)]-1n+2.展开更多
Let Mn be an n-dimensional complete connected and oriented hypersurface in a hyperbolic space H(n+1)(c) with non-zero constant mean curvature H and two distinct principal curvatures. In this paper, we show that ...Let Mn be an n-dimensional complete connected and oriented hypersurface in a hyperbolic space H(n+1)(c) with non-zero constant mean curvature H and two distinct principal curvatures. In this paper, we show that (1) if the multiplicities of the two distinct principal curvatures are greater than 1,then Mn is isometric to the Riemannian product Sk(r)×H(n-k)(-1/(r2 + ρ2)), where r 〉 0 and 1 〈 k 〈 n - 1;(2)if H2 〉 -c and one of the two distinct principal curvatures is simple, then Mn is isometric to the Riemannian product S(n-1)(r) × H1(-1/(r2 +ρ2)) or S1(r) × H(n-1)(-1/(r2 +ρ2)),r 〉 0, if one of the following conditions is satisfied (i) S≤(n-1)t22+c2t(-2)2 on Mn or (ii)S≥ (n-1)t21+c2t(-2)1 on Mn or(iii)(n-1)t22+c2t(-2)2≤ S≤(n-1)t21+c2t(-2)1 on Mn, where t_1 and t_2 are the positive real roots of (1.5).展开更多
This paper discusses the existence problem in the study of some partial differential equations. The author gets some bifurcation on the prescribed mean curvature problem on the unit ball, the scalar curvature problem ...This paper discusses the existence problem in the study of some partial differential equations. The author gets some bifurcation on the prescribed mean curvature problem on the unit ball, the scalar curvature problem on the n-sphere, and some field equations. The author gives some natural conditions such that the standard bifurcation or Thom-Mather theory can be used.展开更多
文摘In this paper,we study the complete space-like submanifold Mn with constant scalar curvature R≤c in the de Sitter space Spn+p(c) and obtain a pinching condition for Mn to be totally umbilical ones.The result generalizes that in [5,Main Theorem] to higher codimension and give a complement for n=2 there.
文摘Goldberg and Wu studied a conformally flat manifold M with constant scalar curvature. When the Ricci curvature of M is of bounded below or positive,the conditions of M becoming a constant curvature manifold are obtained. In this paper,we consider conharmonically flat manifolds and quasi conformally flat manifolds with constant saclar curvature. The corresponding results are generalized.
基金supported by Foundation of Natural Sciences of China(11671121,11871197 and 11431009)。
文摘Let E_(s)^(m+p+1) ?R_(s+1)^(m+p+2)(m≥ 2,p≥ 1,0≤s≤p) be the standard(punched)light-cone in the Lorentzian space R_(s+1)^(m+p+2),and let Y:M^(m)→E_(s)^(m+p+1) be a space-like immersed submanifold of dimension m.Then,in addition to the induced metric g on Mm,there are three other important invariants of Y:the Blaschke tensor A,the conic second fundamental form B,and the conic Mobius form C;these are naturally defined by Y and are all invariant under the group of rigid motions on E_(s)^(m+p+1).In particular,g,A,B,C form a complete invariant system for Y,as was originally shown by C.P.Wang for the case in which s=0.The submanifold Y is said to be Blaschke isoparametric if its conic Mobius form C vanishes identically and all of its Blaschke eigenvalues are constant.In this paper,we study the space-like Blaschke isoparametric submanifolds of a general codimension in the light-cone E_(s)^(m+p+1) for the extremal case in which s=p.We obtain a complete classification theorem for all the m-dimensional space-like Blaschke isoparametric submanifolds in Epm+p+1of constant scalar curvature,and of two distinct Blaschke eigenvalues.
文摘The following article has been retracted due to the investigation of complaints received against it. Mr. Mohammadali Ghorbani (corresponding author and also the last author) cheated the authors’ name: Alireza Heidari, Foad Khademi,Jahromi and Roozbeh Amiri. The scientific community takes a very strong view on this matter and we treat all unethical behavior such as plagiarism seriously. This paper published in Vol.3 No.4 334-339, 2012, has been removed from this site.
基金Project supported by the Stress Supporting Subject Foundation of Zhejiang Province, China
文摘Let Mn be a closed submanifold isometrically immersed in a unit sphere Sn . Denote by R, H and S, the normalized +p scalar curvature, the mean curvature, and the square of the length of the second fundamental form of Mn, respectively. Suppose R is constant and ≥1. We study the pinching problem on S and prove a rigidity theorem for Mn immersed in Sn +pwith parallel nor- malized mean curvature vector field. When n≥8 or, n=7 and p≤2, the pinching constant is best.
文摘Let Mn be a closed spacelike submanifold isometrically immersed in de Sitter space S^n+p _p(c).Denote by R,H and S the normalized scalar curvature,the mean curvature and the square of the length of the second fundamental form of Mn,respectively.Suppose R is constant and R≤c. The pinching problem on S is studied and a rigidity theorem for Mn immersed in ~S^n+p _p(c) with parallel normalized mean curvature vector field is proved.When n≥3, the pinching constant is the best.Thus,the mistake of the paper “Space-like hypersurfaces in de Sitter space with constant scalar curvature”(see Manus Math,1998,95:499-505) is corrected.Moreover,the reduction of the codimension when Mn is a complete submanifold in S^n+p _p(c) with parallel normalized mean curvature vector field is investigated.
文摘We consider a similarity kinematic of a deltoid by studying locally the scalar curvature for the corresponding two dimensional kinematic surfaces in the Euclidean space . We prove that there is no two dimensional kinematic surfaces with scalar curvature K is non-zero constant. We describe the equations that govern such the surfaces.
文摘Under the assumption that the normalized mean curvature vector is parallel in the normal bundle, by using the generalized ChengYau's self-adjoint differential operator, here we obtain some rigidity results for compact submanifolds with constant scalar curvature and higher codimension in the space forms.
文摘Let f: Mn(?)Sn+1 C Rn+2 be an n-dimensional complete oriented Rieman-nian manifold minimally immersed in an (n+1)-dimensional unit sphere Sn+1. Denote by S_+~n+1 the upper closed hemisphere. If f(Mn)(?)_+~n+1, then under some curvature conditions the authors can get that the isometric immersion is a totally embedding. They also generalize a theorem of Li Hai Zhong on hypersurface of space form with costant scalar curvature.
基金Supported by the National Natural Science Foundation of China(11071005)Research Fund for the Doctoral Program of Higher Education of China 20110001110069
文摘A Finsler metric on a manifold M with its flag curvature K is said to be almost isotropic flag curvature if K = 3c + δ where δ and c are scalar functions on M. In this paper, we establish the intrinsic relation between scalar functions c(x) and a(x). More general, by invoking the Ricci identities for a one form, we investigate Finsler metric of weakly isotropic flag curvature K = 3θ/F + δ and show that F has constant flag curvature if θ is horizontally parallel.
文摘In this paper we consider the homothetic motion of Lorentzian circle by studying the scalar curvature for the corresponding cyclic surface locally. We prove that if the scalar curvature is constant, then . We describe the equations that govern such surfaces.
基金Supported by the NSF of China(10671087)Supported by the NSF of Jiangxi Province(2008GZS0024)
文摘The most important Moebius invariants in the Moebius differential geometry of submanifolds in S^n+p are the Moebius metric g, the Moebius second fundamental form B, the Moebius form φ and the Blaschke tensor A. In this paper, we obtain the upper bound of the Moebius scalar curvature of submanifolds with parallel Moebius form in S^n+p.
文摘In this paper we prove an existence result for the nonlinear elliptic problem:-△u = Ku5,u 〉 0 in Ω,u = 0 on Ω,where Ω is a smooth bounded domain of R3 and K is a positive function in Ω.Our method relies on studying its corresponding subcritical approximation problem and then using a topological argument.
文摘设x:M→An+1是由定义在凸域ΩAn上的某局部严格凸函数xn+1=f(x1,...,xn)给出的超曲面.考虑Hessian度量 g =∑2fxixjdxidxj.若(M,g)是具有非负李奇曲率的紧致Hessian流形且仿射Khler-Scalar曲率为零,作者证明了如果Δρ≤nρ2,则函数f一定是二次多项式,其中ρ=[det(fij)]-1n+2.
基金supported by NSF of Shaanxi Province (SJ08A31)NSF of Shaanxi Educational Committee (2008JK484+1 种基金2010JK642)Talent Fund of Xi'an University of Architecture and Technology
文摘Let Mn be an n-dimensional complete connected and oriented hypersurface in a hyperbolic space H(n+1)(c) with non-zero constant mean curvature H and two distinct principal curvatures. In this paper, we show that (1) if the multiplicities of the two distinct principal curvatures are greater than 1,then Mn is isometric to the Riemannian product Sk(r)×H(n-k)(-1/(r2 + ρ2)), where r 〉 0 and 1 〈 k 〈 n - 1;(2)if H2 〉 -c and one of the two distinct principal curvatures is simple, then Mn is isometric to the Riemannian product S(n-1)(r) × H1(-1/(r2 +ρ2)) or S1(r) × H(n-1)(-1/(r2 +ρ2)),r 〉 0, if one of the following conditions is satisfied (i) S≤(n-1)t22+c2t(-2)2 on Mn or (ii)S≥ (n-1)t21+c2t(-2)1 on Mn or(iii)(n-1)t22+c2t(-2)2≤ S≤(n-1)t21+c2t(-2)1 on Mn, where t_1 and t_2 are the positive real roots of (1.5).
基金This work is partially supported by NNSF of ChinaSRF for Returned Overseas Chinese Scholars+1 种基金State Education Commission a scientific grant of Tsinghua University at Beijing
文摘This paper discusses the existence problem in the study of some partial differential equations. The author gets some bifurcation on the prescribed mean curvature problem on the unit ball, the scalar curvature problem on the n-sphere, and some field equations. The author gives some natural conditions such that the standard bifurcation or Thom-Mather theory can be used.