一个从多重特征值出发的分歧定理

讨论非线性方程F(λ,u)=0的分歧问题,这里F:R×X→Y为非线性微分映射,X,Y为Banach空间,利用Lyapunov-Schmidt约化过程和隐函数定理证得一个从多重特征值出发的分歧定理.推广了Crandall M G与Rabinowitz P H的经典分歧定理.     

A Minimax Principle for the Eigenvalues in Spectral Gaps

A minimax principle is derived for the eigenvalues in the spectralgap of a possibly non-semibounded self-adjoint operator. Itallows the nth eigenvalue of the Dirac operator with Coulombpotential from below to be bound by the nth eigenvalue of asemibounded Hamiltonian which is of interest in the contextof stability of matter. As a second application it is shownthat the Dirac operator with suitable non-positive potentialhas at least as many discrete eigenvalues as the Schrödingeroperator with the same potential.     

A New Fourth-order Finite-difference Method for Computing Eigenvalues of Fourth-order Two-point Boundary-value Problems

We present a new finite-difference method for computing eigenvaluesof two-point boundary-value problems involving a fourth-orderdifferential equation. Our finite-difference method leads toa generalized seven-diagonal symmetric-matrix eigenvalue problemand provides O(h⁴)-convergent approximations for the eigenvalues.     

Isotropy Representations, Eigenvalues of a Casimir Element, and Commutative Lie Subalgebras

Let h be a reductive subalgebra of a semisimple Lie algebrag and C_h U(h) be the Casimir element determined by the restrictionof the Killing form on g to h. The paper studies eigenvaluesof C_h on the isotropy representation mg/h. Some general estimatesconnecting the eigenvalues and the Dynkin indices of m are given.If h is a symmetric subalgebra, it is shown that describingthe maximal eigenvalue of C_h on exterior powers of m is connectedwith possible dimensions of commutative Lie subalgebras in m,thereby extending a result of Kostant. In this situation, aformula is also given for the maximal eigenvalue of C_h on m.More generally, a similar picture arises if h = g, where isan automorphism of finite order m and m is replaced by the eigenspaceof corresponding to a primitive mth root of unity.     

Realistic a Priori and a Posteriori Error Bounds for Computed Eigenvalues

Permanent address: Department of Engineering Mathematics, Cairo University, Giza, Egypt. A priori and a posteriori error bounds are given for the computedeigenpair (, ) of the eigenvalue problem Ax = x, which are shownto be more realistic than some of the available ones. A simplemethod is also presented for computing the backward error. Finallya scaling procedure is explained for reducing the residual error.     

Several Abstract Iterative Schemes for Solving the Bifurcation at Simple Eigenvalues

In this paper we consider the nonlinear operator equation $\lambda x=Lx+G(\lambda,x)$ where $L$ is a closed linear operator of $X-›X, X$ is a real Banach Space, with a simple eigenvalue $\lambda_0\neq 0$. We discretize its Liapunov-Schmidt bifurcation equation instead of the original nonlinear operator equation and estimate the approximating order of our approximate solution to the genuine solution. Our method is more convenient and more accurate. Meanwhile we put forward several abstract Newton-type iterative schemes, which are more efficient for practical computation, and get the result of their super-linear convergence.     

On the Multiplicities of Graph Eigenvalues

Star complements and associated quadratic functions are usedto obtain a sharp upper bound for the order of a graph withan eigenspace of prescribed codimension. It is shown that forregular graphs the bound can be reduced by 1, and that thisreduced bound is attained by a regular graph G if and only ifG is an extremal strongly regular graph. 2000 Mathematics SubjectClassification 05C50.     

Approximation of Ground State Eigenvalues and Eigenfunctions of Dirichlet Laplacians

Let be a bounded connected open set in R^N, N 2, and let –0be the Dirichlet Laplacian defined in L²(). Let > 0 be thesmallest eigenvalue of –, and let > 0 be its correspondingeigenfunction, normalized by ||||₂ = 1. For sufficiently small>0 we let R() be a connected open subset of satisfying Let – 0 be the Dirichlet Laplacian on R(), and let >0and >0 be its ground state eigenvalue and ground state eigenfunction,respectively, normalized by ||||₂=1. For functions f definedon , we let Sf denote the restriction of f to R(). For functionsg defined on R(), we let Tg be the extension of g to satisfying 1991 Mathematics SubjectClassification 47F05.     

Optimal Shape Problems for Eigenvalues

ABSTRACT

We consider the first Dirichlet eigenvalue for nonhomogeneous membranes. For given volume we want to find the domain which minimizes this eigenvalue. The problem is formulated as a variational free boundary problem. The optimal domain is characterized as the support of the first eigenfunction. We prove enough regularity for the eigenfunction to conclude that the optimal domain has finite parameter. Finally an overdetermined boundary value problem on the regular part of the free boundary is given.     

More on Graph Perturbations

Various modifications of a connected graph G are regarded asperturbations of an adjacency matrix A of G. Several resultsconcerning the resulting changes to the largest eigenvalue ofA are obtained by solving intermediate eigenvalue problems ofthe second type.     

Principal Eigenvalues for Generalised Indefinite Robin Problems

We consider the principal eigenvalue of generalised Robin boundary value problems on non-smooth domains, where the zero order coefficient of the boundary operator is negative or changes sign. We provide conditions so that the related eigenvalue problem has a principal eigenvalue. We work with the framework involving measure data on the boundary due to Arendt and Warma (Potential Anal 19:341–363, 2003). Examples of simple domains with cusps are used to illustrate all possible phenomena.     

Eigenvalues and expanders

Linear expanders have numerous applications to theoretical computer science. Here we show that a regular bipartite graph is an expanderif and only if the second largest eigenvalue of its adjacency matrix is well separated from the first. This result, which has an analytic analogue for Riemannian manifolds enables one to generate expanders randomly and check efficiently their expanding properties. It also supplies an efficient algorithm for approximating the expanding properties of a graph. The exact determination of these properties is known to be coNP-complete. The research was supported by the Weizmann Fellowship for Scientific Research and by Air Force Contract OSR 82-0326.     

Eigenvalues and colorings of digraphs

Wilf’s eigenvalue upper bound on the chromatic number is extended to the setting of digraphs. The proof uses a generalization of Brooks’ Theorem to digraph colorings.     

Multiple bifurcation from “simple” eigenvalues

Consider an operator equation G(u,λ) = 0 where λ is a real parameter. Suppose 0 is a “simple” eigenvalue of the Fréchet derivative G_u at (u₀, λ₀). We give a hierarchy of conditions which completely determines the solution structure of the operator equation. It will be shown that multiple bifurcation as well as simple bifurcation can occur. This extends the standard bifurcation theory from a simple eigenvalue in which only one branch bifurcates. We also discuss limit point bifurcations. Applications to semilinear elliptic equations and the homotopy method for the matrix eigenvalue problem are also given.     

A continuation method for a weakly elliptic two-parameter eigenvalue problem

We show that the continuation method can be used to solve aweakly elliptic two-parameter eigenvalue problem. We generalizethe continuation method for a nonsymmetric eigenvalue problemAx = x by T. Y. Li, Z. Zeng and L. Cong (1992 SIAM J. Numer.Anal. 29, 229–248) to two-parameter problems.     

Regular Graphs,Eigenvalues and Regular Factors

In this article, we obtain a sufficient condition for the existence of regular factors in a regular graph in terms of its third largest eigenvalue. We also determine all values of k such that every r‐regular graph with the third largest eigenvalue at most has a k‐factor.     

Numerical analysis of subspace-breaking Takens-Bogdanov points

It is assumed that a two-parameter-dependent family of smoothvector fields on R^N leaves a proper subspace u of R^N invariant.Takens-Bogdanov bifurcation points on u are considered. Computationof these points together with their computer-aided asymptoticanalysis are discussed. The asymptotic formulae are appliedas analytical predictors of, for example, Hopf bifurcation pointsthat emanate from a detected Takens-Bogdanov point. Anotherapplication is a local stability analysis of imperfect bifurcationdiagrams.     

典型几何上Ricci流下的特征值

研究了典型几何上规范Ricci流下Laplace-Beltrami算子第一特征值的发展行为.在每一个Bianchi类中,我们估计了特征值的导数.构造了Ricci流下的单调量并得到了特征值的上下界估计.     

勒让德方程本征值的确定

大部分数学物理方法教材直接给出了勒让德方程本征值的表达式,比较突兀,学生也难以理解.为消除学生在此处的学习障碍,直接从勒让德方程的一般形式入手,通过常点邻域的级数解法,推导出勒让德方程本征值的表示形式.     

Eigenvalues of Random Power law Graphs

Many graphs arising in various information networks exhibit the "power law" behavior -the number of vertices of degree k is proportional to k^-# for some positive #. We show that if # > 2.5, the largest eigenvalue of a random power law graph is almost surely(1+ o(1))?m (1+ o(1))\sqrt{m} where m is the maximum degree. Moreover, the klargest eigenvalues of a random power law graph with exponent # have power law distribution with exponent 2# if the maximum degree is sufficiently large, where k is a function depending on #, mand d, the average degree. When 2<#< 2.5, the largest eigenvalue is heavily concentrated at cm^3-# for some constant c depending on # and the average degree. This result follows from a more general theorem which shows that the largest eigenvalue of a random graph with a given expected degree sequence is determined by m, the maximum degree, and [(d)\tilde] \tilde{d} , the weighted average of the squares of the expected degrees. We show that the k-th largest eigenvalue is almost surely (1+ o(1))?{m_k} (1+ o(1))\sqrt{m_k} where m_k is the k-th largest expected degree provided m_k is large enough. These results have implications on the usage of spectral techniques in many areas related to pattern detection and information retrieval.