共查询到20条相似文献,搜索用时 93 毫秒
1.
本文定义了非重交换的联合半亚正常算子组,证明了谱分割定理和谱投影定理,提示了半亚正常算子组的 Taylor 联合谱与它们的记号算子组的 Taylor 联合谱之间的关系. 相似文献
2.
给出了关于算子组Taylor谱的另一种定义及ε-联合伪谱的定义,并讨论了它的一些性质以及关于交叉交换算子组在这几种定义下的一些结果. 相似文献
3.
4.
5.
本文主要研究了 Banach 空间上交换算子组的张量积以及 Banach 代数的张量积中交换元组的 Taylor 联合谱,推广了 Vasilescu,F.H.及 Wrobel,V.等人结果。 相似文献
6.
只有纯虚谱的Hamilton算子 总被引:1,自引:1,他引:0
刻画了一类无穷维Hamilton算子的谱的分布情况,并得到了无穷维Hamilton算子只有纯虚谱的充分条件.最后,构造出具体的例子以说明判别准则的有效性. 相似文献
7.
本文讨论了算子A∈B(H)N为算子T∈B(H)的算子点谱的判定条件,特别得到:当T为亚正常算子时,A为T的算子点谱的判定条件,另外还得到kerτnT,A=kerτT,A成立的充分条件 相似文献
8.
9.
证明了 :在自反 Banach空间$X$中 ,每个闭子空间 L,都存在 X到 L上的拟线性投影算子 SL.一般说来 ,SL 既非度量投影算子 ,又非线性算子 . 相似文献
10.
11.
The aim of this paper is to describe the closure of the numerical range of the product of two orthogonal projections in Hilbert space as a closed convex hull of some explicit ellipses parametrized by points in the spectrum. Several improvements (removing the closure of the numerical range of the operator, using a parametrization after its eigenvalues) are possible under additional assumptions. An estimate of the least angular opening of a sector with vertex 1 containing the numerical range of a product of two orthogonal projections onto two subspaces is given in terms of the cosine of the Friedrichs angle. Applications to the rate of convergence in the method of alternating projections and to the uncertainty principle in harmonic analysis are also discussed. 相似文献
12.
A. V. Kel’manov L. V. Mikhailova S. A. Khamidullin 《Computational Mathematics and Mathematical Physics》2008,48(12):2276-2288
The problem of joint detection of a recurring tuple of reference fragments in a noisy numerical quasi-periodic sequence is solved in the framework of the a posteriori (off-line) approach. It is assumed that (i) the total number of fragments in the sequence is known, (ii) the index of the sequence member corresponding to the beginning of a fragment is a deterministic (not random) value, and (iii) a sequence distorted by an additive uncorrelated Gaussian noise is available for observation. It is shown that the problem consists of testing a set of simple hypotheses about the mean of a random Gaussian vector. A specific feature of the problem is that the cardinality of the set grows exponentially as the vector dimension (i.e., the length of the observed sequence) and the number of fragments in the sequence increase. It is established that the search for a maximum-likelihood hypothesis is equivalent to the search for arguments that maximize a special auxiliary objective function with linear inequality constraints. It is shown that this function is maximized by solving the basic extremum problem. It is proved that this problem is solvable in polynomial time. An exact algorithm for its solution is substantiated that underlies an algorithm guaranteeing optimal (maximum-likelihood) detection of a recurring tuple of reference fragments. The results of numerical simulation demonstrate the noise stability of the detection algorithm. 相似文献
13.
设U,V是Hilbert空间H的两个闭子空间.若存在H的闭子空间L满足L+U=H,L+V=H,且L∩U=L∩V={0},则称L是U和V的公共补.本文获得了两子空间有公共补的一些新的特征,给出了等式H=[U∩(U⊥+ V⊥)]⊕[V⊕(U⊥∩V⊥)]成立的充分必要条件,完全回答了GroB提出的问题. 相似文献
14.
15.
The cyclic projections algorithm is an important method for determining a point in the intersection of a finite number of closed convex sets in a Hilbert space. That is, for determining a solution to the “convex feasibility” problem. This is the third paper in a series on a study of the rate of convergence for the cyclic projections algorithm. In the first of these papers, we showed that the rate could be described in terms of the “angles” between the convex sets involved. In the second, we showed that these angles often had a more tractable formulation in terms of the “norm” of the product of the (nonlinear) metric projections onto related convex sets.In this paper, we show that the rate of convergence of the cyclic projections algorithm is also intimately related to the “linear regularity property” of Bauschke and Borwein, the “normal property” of Jameson (as well as Bakan, Deutsch, and Li’s generalization of Jameson’s normal property), the “strong conical hull intersection property” of Deutsch, Li, and Ward, and the rate of convergence of iterated parallel projections. Such properties have already been shown to be important in various other contexts as well. 相似文献
16.
This paper presents necessary and sufficient conditions for a positive bounded operator on a separable Hilbert space to be the sum of a finite or infinite collection of projections (not necessarily mutually orthogonal), with the sum converging in the strong operator topology if the collection is infinite. A similar necessary condition is given when the operator and the projections are taken in a type II von Neumann factor, and the condition is proven to be also sufficient if the operator is “diagonalizable”. A simpler necessary and sufficient condition is given in the type III factor case. 相似文献
17.
Alexander Pushnitski 《Journal of Functional Analysis》2011,261(7):2053-2081
Let H0 and H be self-adjoint operators in a Hilbert space. We consider the spectral projections of H0 and H corresponding to a semi-infinite interval of the real line. We discuss the index of this pair of spectral projections and prove an identity which extends the Birman-Schwinger principle onto the essential spectrum. We also relate this index to the spectrum of the scattering matrix for the pair H0, H. 相似文献
18.
We study the properties of the polynomial operator pencil
, where
is ak-dimensional Hilbert space, and prove that the mixed discriminants {d
j
}
j=0
nk
, defined as the coefficients of the polynomial
, are completely determined by the joint spectrum of the family {M
i
}
i=0
n
. A generalization of Gershgorin's well-known theorem on the position of the eigenvalues of a matrix to the case of a polynomial
matrix pencil is obtained.
Translated by V. E. Nazaikinskii
Translated fromMatematicheskie Zametki, Vol. 62, No. 1, pp. 3–9, July, 1997. 相似文献
19.
Timur Oikhberg 《Proceedings of the American Mathematical Society》1999,127(12):3659-3669
We give a characterization of operators on a separable Hilbert space of norm less than one that can be represented as products of orthogonal projections and give an estimate on the number of factors. We also describe the norm closure of the set of all products of orthogonal projections.
20.
Harald K. Wimmer 《Proceedings of the American Mathematical Society》2000,128(3):873-876
Let and be complementary spaces of a finite dimensional unitary space and let denote the projection of on parallel to . Estimates for the norm of are derived which involve the norm of the restriction of to or the gap between and .