Results 71 to 80 of about 3,267 (95)

Perturbation theory for a linear operator

Mathematical Proceedings of the Cambridge Philosophical Society, 1967
AbstractWe extend certain results of the theory of closed operators in Banach spaces to general linear operators in normed spaces. A ‘state diagram’ for linear operators is drawn up. We prove some perturbation theorems, improving or correcting certain results of Goldberg.
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Connection between perturbation theory, projection-operator techniques, and statistical linearization for nonlinear systems

Physical Review A, 1978
We employ the equivalence between Zwanzig's projection-operator formalism and perturbation theory to demonstrate that the approximate-solution technique of statistical linearization for nonlinear stochastic differential equations corresponds to the lowest-order ..beta..
Aaron B. Budgor, Bruce J. West
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Spectral Theory for Perturbations of Unbounded Linear Operators

2016
In this chapter we first study the spectral theory of completely continuous perturbations of unbounded Fredholm operators in the non-archimedean Hilbert space \( \mathbb{E}_{\omega } \).
Toka Diagana, François Ramaroson
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Perturbation of the spectrum and wave operators in linear transport theory

Russian Mathematical Surveys, 1999
Summary: We study spectral properties of a nonself-adjoint integro-differential operator \[ L=L_0+iV=i\mu\;\frac{\partial}{\partial x}+ic(x)\int^1_{-1}\cdot\;d\mu \] acting on the space \({\mathcal H}= L^2(\mathbb{R}\times [-1,1])\), with domain \(\{\psi\in{\mathcal H}:\psi(\cdot,\mu)\) absolutely continuous for almost all \(\mu\in[-1,1]\), \(L_0\psi ...
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Low-order scaling local correlation methods II: Splitting the Coulomb operator in linear scaling local second-order Møller–Plesset perturbation theory

The Journal of Chemical Physics, 2000
A novel multipole approximation for the linear scaling local second-order Møller–Plesset perturbation theory (MP2) method is presented, which is based on a splitting of the Coulomb operator into two terms. The first one contains the singularity and is rapidly decaying with increasing distance. It is treated by a conventional two-electron transformation,
Georg Hetzer, Martin Schütz, Hermann Stoll, Hans-Joachim Werner   +3 more
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Spectral Theory for Perturbations of Bounded Diagonal Linear Operators

2016
Our main goal in this chapter consists of computing the spectrum of the class of bounded linear operators, \( A = D + F \) where D is a diagonal operator and F is a finite rank operator. In order to achieve that, we will make extensive use of the theory of Fredholm operators and the notion of essential spectrum.
Toka Diagana, François Ramaroson
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Methods of abstract harmonic analysis in the perturbation of linear operators

Siberian Mathematical Journal, 1983
The basic results of the paper refer to questions of similarity of a certain class of non-self-adjoint operators. Methods of abstract harmonic analysis for operators from certain group algebras connected with an unperturbed operator are used. Applications are criteria for the spectrality of perturbed spectral operators with discrete spectrum ...
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An abstract analog of the krylov-bogolyubov transformation in the perturbation theory of linear operators

Functional Analysis and Its Applications, 1999
UDC 517.9 Let ~'be a Bmlach space over a field K E {R,C}, and let B(a,p) be the open ball in ~'with center a E ~" and radius p > 0. By Lipk(~ a, p), k E NU {0}, we denote the Banach space of continuous mappings (operators) defined on the closed ball B(a, p) = B(a, p), ranging in ~'.
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Perturbation of differential operators on high-codimension manifold and the extension theory for symmetric linear relations in an indefinite metric space

Theoretical and Mathematical Physics, 1992
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Perturbation Theory for Linear Operators

2021
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