共查询到20条相似文献,搜索用时 343 毫秒
1.
Lu Changyu 《东北数学》1994,(3)
ANecessaryandSufficientConditionforAdmissibilityofNonnegativeQuadraticEstimatorLuChangyu(鹿长余)(DepartmentofMathematics,Northea... 相似文献
2.
Jian Zhong PAN Shao Bing WU 《数学学报(英文版)》2006,22(1):23-26
in this note, we answer positively a question by Belegradek and Kapovitch about the relation between rational homotopy theory and a problem in Riemannian geometry which asks that total spaces of which vector bundles over compact non-negative curved manifolds admit (complete) metrics with non-negative curvature. 相似文献
3.
In this paper, we study complete open manifolds with nonnegative Ricci curvature and injectivity radius bounded from below. We find that this kind of manifolds are diffeomorphic to a Euclidean space when certain distance functions satisfy a reasonable condition. 相似文献
4.
Hong-zhou Wang Li-hu Deng Wei-gao GeDepartment of Applied Mathematics Beijing Institute of Technology Beijing China 《应用数学学报(英文版)》2002,18(3):523-528
In this paper we study a class of semi-positone singular boundary value problem. With prior bounds estimate and topology degree method, some existence results of nonnegative solution will be shown. 相似文献
5.
Simone Naldi 《Discrete and Computational Geometry》2014,51(3):559-568
In 1888 Hilbert showed that every nonnegative homogeneous polynomial with real coefficients of degree $2d$ in $n$ variables is a sum of squares if and only if $d=1$ (quadratic forms), $n=2$ (binary forms) or $(n,d)=(3,2)$ (ternary quartics). In these cases, it is interesting to compute canonical expressions for these decompositions. Starting from Carathéodory’s Theorem, we compute the Carathéodory number of Hilbert cones of quadratic forms and binary forms. 相似文献
6.
Potential Analysis - In this paper we present a short proof of the following classification Theorem for g ?harmonic functions in half-spaces. Assume that u is a nonnegative solution to... 相似文献
7.
Given any nonnegative matrix $A \in \mathbb{R}^{m \times n}$ , it is always possible to express A as the sum of a series of nonnegative rank-one matrices. Among the many possible representations of A, the number of terms that contributes the shortest nonnegative rank-one series representation is called the nonnegative rank of A. Computing the exact nonnegative rank and the corresponding factorization are known to be NP-hard. Even if the nonnegative rank is known a priori, no simple procedure exists presently that is able to perform the nonnegative factorization. Based on the Wedderburn rank reduction formula, this paper proposes a heuristic approach to tackle this difficult problem numerically. Starting with A, the idea is to recurrently extrat, whenever possible, a rank-one nonnegative portion from the previous matrix while keeping the residual nonnegative and lowering its rank by one. With a slight modification for symmetry, the method can equally be applied to another important class of completely positive matrices. No convergence can be guaranteed, but repeated restart might help alleviate the difficulty. Extensive numerical testing seems to suggest that the proposed algorithm might serve as a first-step numerical means for exploring the intriguing problem of nonnegative rank factorization. 相似文献
8.
Let x : M→S^n+1 be a hypersurface in the (n + 1)-dimensional unit sphere S^n+1 without umbilic point. The Mobius invariants of x under the Mobius transformation group of S^n+1 are Mobius metric, Mobius form, Mobius second fundamental form and Blaschke tensor. In this paper, we prove the following theorem: Let x : M→S^n+1 (n≥2) be an umbilic free hypersurface in S^n+1 with nonnegative Mobius sectional curvature and with vanishing Mobius form. Then x is locally Mobius equivalent to one of the following hypersurfaces: (i) the torus S^k(a) × S^n-k(√1- a^2) with 1 ≤ k ≤ n - 1; (ii) the pre-image of the stereographic projection of the standard cylinder S^k × R^n-k belong to R^n+1 with 1 ≤ k ≤ n- 1; (iii) the pre-image of the stereographic projection of the Cone in R^n+1 : -↑x(u, v, t) = (tu, tv), where (u,v, t)∈S^k(a) × S^n-k-1( √1-a^2)× R^+. 相似文献
9.
In this paper, by the method of upper and lower solutions, we establish the existence of the non-trivial nonnegative periodic solutions for a class of degenerate diffusion system arising from dynamics of biological groups. 相似文献
10.
Mei Jiaqiang Xu Senlin 《东北数学》1998,(3)
AlmostFlatTheoremforCompleteOpenRiemannianManifoldswithNonnegativeRicciCurvature*)MeiJiaqiang(梅加强)XuSenlin(徐森林)(DepartmentofM... 相似文献
11.
The aim of this paper is to establish two Radon–Nikodym-type theorems for nonnegative Hermitian forms defined on a real or complex vector space and to apply these results to provide some known Radon–Nikodym-type theorems of the theory of representable positive functionals, \(\sigma \)-additive and finitely additive measures. 相似文献
12.
Michael Munn 《Journal of Geometric Analysis》2010,20(3):723-750
Let M n be a complete, open Riemannian manifold with Ric≥0. In 1994, Grigori Perelman showed that there exists a constant δ n >0, depending only on the dimension of the manifold, such that if the volume growth satisfies \(\alpha_{M}:=\lim_{r\rightarrow \infty}\frac{\operatorname{Vol}(B_{p}(r))}{\omega_{n}r^{n}}\geq 1-\delta_{n}\), then M n is contractible. Here we employ the techniques of Perelman to find specific lower bounds for the volume growth, α(k,n), depending only on k and n, which guarantee the individual k-homotopy group of M n is trivial. 相似文献
13.
Xiao-ning Lin Hai-yin Gao 《应用数学学报(英文版)》2005,21(3):405-414
The existence of multiple nonnegative solutions for singular positone boundary value problems to the delay one-dimension p-Laplacian is discussed in this paper. 相似文献
14.
《数学研究与评论》1992,(1)
We consider the spaces∧_αof Lipschitz continuous functions on completeRiemannian manifold with nonnegative Ricci curvature.We first give a characeriza-tion of f∈∧_αin terms of its Poisson integral u(x,t),then we show that the BesselPotential J_βmaPPs∧_αisomorphically onto∧_(α+β). 相似文献
15.
Let ψ(r) is a positive function on [0, ∞),ψ(r)∞(r→∞), andLet φ is such function family that if φ(z)∈φ, then φ(z) is analytic in thesemi-plane Rez>0, continuous on Rez≥0, φ(z)≠0, and 相似文献
16.
Olga Taussky Alfred P. Sloan 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1979,30(2):370-373
Matrices and operators of the formA
–1
A
* have received a certain amount of attention in recent years. Here some of the literature is surveyed and the caseA
–1
A is studied for complex matrices withA denoting the transpose ofA. A generalization ofA
–1
A is introduced.
Dedicated to Eduard Stiefel by a long time admirer 相似文献
Zusammenfassung Matrizen und Operatoren, die in der FormA –1 A * ausgedrückt werden können, sind in den letzten Jahren häufig studiert worden. Hier wird ein Ueberblick über Teil der relevanten Literatur gegeben und auch der FallA –1 A für komplexe Matrizen studiert, wobeiA die Transponierte vonA ist. Es wird auch eine Verallgemeinerung vonA –1 A eingeführt.
Dedicated to Eduard Stiefel by a long time admirer 相似文献
17.
<正> In my paper entitled'On the Poincaré's groups and the extendeduniversal coverings of closed orientable two-manifolds”,the conversepart of (i) of Number 7 is not valid and should be omitted.The firstplace where this conve(?)se part was used is in the proof of(iii)ofNumber 7.To make the correction,at the end of(i)of Number 5 wereplace“not reduced.”by“not reduced, but (u_(1,1)) (u_(1,2))is reduced”,and to(iii)of Number 5 we add“When u_(1,2) is not the(2p-1)st f.e. 相似文献
18.
Asiswellknown,nonlineartwo-pointboundaryvalueproblemisaclassicalbasicproblem.Theresultsofthisproblemareusuallyratherperfect.But,somenewproofsandimprovementsoftheseresultswillbeverymeaningfulandprofittherelatedproblem.Considerthefollowingboundaryvalueproblemwhereh(t,xl,x2)andf(t,xl,x2)arecontinuous,f(t,xl)x2)isboundedfortE[0,r],--co相似文献
19.
In the paper conditions are found under which the A-structure on the homology of a differential algebra degenerates. Examples of such algebras are given. In particular, it is shown that the A-algebra structure on the Milnor coalgebra degenerates, and that if the cohomology of a topological space is a polynomial algebra, then the A-algebra structure on it degenerates. 相似文献
20.
This note simplifies Cordoba-Fefferman's proof on the weak boundedness of strong maximal operator M_8 (with respect to dμ) on L(1+log~(+(n-1))L). Some two-weighted boundedness results on L(1+log~(+α)L) of M_8 are investigated. 相似文献