Coperturbation function and lower semi-Browder multivalued linear operators

In this article, we investigate the perturbation theory of lower semi-Browder and Browder linear relations. Our approach is based on the concept of a coperturbation function for linear relations in order to establish some perturbation theorems and deduce the stability under strictly cosingular operator perturbations. Furthermore, we apply the obtained results to study the invariance and the characterization of Browder's essential defect spectrum and Browder's essential spectrum.     

Riesz operators and the complete norm topology

We show that a non-injective Riesz operator on an infinite-dimensional Banach space X does not determine the complete norm topology of X. We also show that an injective operator with trivial generalized range determines the complete norm topology of X. Finally this result is used to settle the crucial role of the non-injectivity condition in our first result.     

Perturbation of normally solvable linear relations in paracomplete spaces

In this paper we investigate the stability of the index, the nullity and the deficiency of normally solvable linear relations in paracomplete spaces under perturbation by strictly singular and T-strictly singular linear relations. This study led us to generalize some well-known results for operators and extend some results of small perturbation of normally solvable linear relations given by T. Alvarez (2012) [3].     

The Riesz basis property of discrete operators and application to a Euler-Bernoulli beam equation with boundary linear feedback control

In this paper, we give an abstract condition of Riesz basisgeneration for discrete operators in Hilbert spaces, from whichwe show that the generalized eigenfunctions of a Euler–Bernoullibeam equation with boundary linear feedback control form a Rieszbasis for the state Hilbert space. As an consequence, the asymptoticexpression of eigenvalues together with exponential stabilityare readily presented.     

Riesz bases for p-subordinate perturbations of normal operators

For a class of unbounded perturbations of unbounded normal operators, the change of the spectrum is studied and spectral criteria for the existence of a Riesz basis with parentheses of root vectors are established. A Riesz basis without parentheses is obtained under an additional a priori assumption on the spectrum of the perturbed operator. The results are applied to two classes of block operator matrices.     

Polynomials generated by linear operators

We study the class of Banach algebra-valued -homogeneous polynomials generated by the powers of linear operators. We compare it with the finite type polynomials. We introduce a topology on similar to the weak topology, to clarify the features of these polynomials.

     

Riesz框架稳定性和摄动的研究

Riesz框架是一种很有特色的含有Riesz基的框架,本文着重研究它的稳定性和摄动,给出了一些有意义的新结果(详见文[1-13]).     

Riesz-type representation for positive linear operators preserving continuity

A Riesz-type representation theorem is given for all positive linear endomorphisms of the space of continuous functions on a compact interval.     

关于B-凸空间及其上黎斯算子West分解

给出 Ｂａｎａｃｈ空间列｛Ｘｉ｝ｉ＝１∞的 ｌｐ乘积Ｂ－凸的特征刻划, 证明Ｂ－凸空间上的每个黎斯算子可Ｗｅｓｔ分解,即分解成一个紧算子和一个拟幂 零算子的和．     

Linear relations in the Calkin algebra for composition operators

We consider this and related questions: When is a finite linear combination of composition operators, acting on the Hardy space or the standard weighted Bergman spaces on the unit disk, a compact operator?

     

A canonical decomposition for linear operators and linear relations

An arbitrary linear relation (multivalued operator) acting from one Hilbert space to another Hilbert space is shown to be the sum of a closable operator and a singular relation whose closure is the Cartesian product of closed subspaces. This decomposition can be seen as an analog of the Lebesgue decomposition of a measure into a regular part and a singular part. The two parts of a relation are characterized metrically and in terms of Stone’s characteristic projection onto the closure of the linear relation.     

Inversion of analytically perturbed linear operators that are singular at the origin

Let H and K be Hilbert spaces and for each z∈C let A(z)∈L(H,K) be a bounded but not necessarily compact linear map with A(z) analytic on a region |z|<a. If A(0) is singular we find conditions under which A⁻¹(z) is well defined on some region 0<|z|<b by a convergent Laurent series with a finite order pole at the origin. We show that by changing to a standard Sobolev topology the method extends to closed unbounded linear operators and also that it can be used in Banach spaces where complementation of certain closed subspaces is possible. Our method is illustrated with several key examples.²     

Gap formulas for closed linear relations

A classical formula for the gap between two densely defined closed operators in a Hilbert space is extended to the case of linear relations. Copyright © 2014 John Wiley & Sons, Ltd.     

Some properties of Riesz potential associated with SchrSdinger operator

Let L = −Δ + V be the Schr?dinger operator on ℝ ^d , d ≥ 3, where Δ is the Laplacian on ℝ ^d and V ≢ 0 is a nonnegative function satisfying the reverse H?lder inequality. In this article, the author investigates some properties of the Riesz potential I _α ^L associated with L on the Campanato-type spaces Λ _L ^β and the Hardy-type spaces H _L ^p .     

Restrictions of bounded linear operators: Closed range

Let be a bounded linear operator on a Banach space and let be a subspace of which is a Banach space and invariant. Denote by the restriction of to This paper explores the questions:

If the range of is closed, under what conditions is the range of closed?

If the range of is closed, under what conditions is the range of closed?

     

Perturbation results for exponentially dichotomous operators on general Banach spaces

Some perturbation results for exponentially dichotomous operators are applied to prove the existence of stable and anti-stable solutions of Riccati equations associated to block operators on general Banach spaces, both for compact perturbations and for bisemigroups made up of immediately norm continuous semigroups.     

Perturbation theory for generalized and constrained linear least squares

The perturbation analysis of weighted and constrained rank‐deficient linear least squares is difficult without the use of the augmented system of equations. In this paper a general form of the augmented system is used to get simple perturbation identities and perturbation bounds for the general linear least squares problem both for the full‐rank and rank‐deficient problem. Perturbation identities for the rank‐deficient weighted and constrained case are found as a special case. Interesting perturbation bounds and condition numbers are derived that may be useful when considering the stability of a solution of the rank‐deficient general least squares problem. Copyright © 2000 John Wiley & Sons, Ltd.