Perturbation results for Stark effect resonances.
Perturbation results on semi-Fredholm operators and applications.
Perturbation series and defect correction for the refinement of approximate eigenelements of linear integral operators
Perturbation theorems for convoluted -semigroups and cosine functions
Perturbation theorems for Hermitian elements in Banach algebras
Two well-known theorems for Hermitian elements in C*-algebras are extended to Banach algebras. The first concerns the solution of the equation ax - xb = y, and the second gives sharp bounds for the distance between spectra of a and b when a, b are Hermitian.
Perturbation theorems for local integrated semigroups
We apply the contraction mapping theorem to establish some bounded and unbounded perturbation theorems concerning nondegenerate local α-times integrated semigroups. Some unbounded perturbation results of Wang et al. [Studia Math. 170 (2005)] are also generalized. We also establish some growth properties of perturbations of local α-times integrated semigroups.
Perturbation theorems for local integrated semigroups and their applications
Motivated by a great deal of interest in operators that may not be densely defined and do not generate global integrated semigroups, we establish general perturbation theorems for local integrated semigroups and describe their applications to local complete second order abstract differential equations.
Perturbation theorems for maximal -regularity
Perturbation theorems of Miyadera type for locally Lipschitz continuous integrated semigroups
A class of perturbing operators for locally Lipschitz continuous integrated semigroups is introduced according to the idea of Miyadera. The paper gives perturbation theorems of Miyadera type for such integrated semigroups.
Perturbation theory and strictly singular operators in locally convex spaces
Perturbation Theory for Dual Semigroups. I. The Sun-Reflexive Case.
Perturbation theory for Schrödinger operators with complex potentials
Perturbation theory relative to a Banach algebra of operators
Let ℬ be a Banach algebra of bounded linear operators on a Banach space X. Let S be a closed linear operator in X, and let R be a linear operator in X. In this paper the spectral and Fredholm theory relative to ℬ of the perturbed operator S + R is developed. In particular, the situation where R is S-inessential relative to ℬ is studied. Several examples are given to illustrate the usefulness of these concepts.
Perturbations by Quadratic Forms and Invariance of Essential Spectra.
Perturbations of bi-continuous semigroups
The notion of bi-continuous semigroups has recently been introduced to handle semigroups on Banach spaces that are only strongly continuous for a topology coarser than the norm-topology. In this paper, as a continuation of the systematic treatment of such semigroups started in [20-22], we provide a bounded perturbation theorem, which turns out to be quite general in view of various examples.
Perturbations of Fredholm operators
Perturbations of normally solvable nonlinear operators. I.
Perturbations of operators satisfying a local growth condition.
Perturbations of operators similar to contractions and the commutator equation
Let T and V be two Hilbert space contractions and let X be a linear bounded operator. It was proved by C. Foiaş and J. P. Williams that in certain cases the operator block matrix R(X;T,V) (equation (1.1) below) is similar to a contraction if and only if the commutator equation X = TZ-ZV has a bounded solution Z. We characterize here the similarity to contractions of some operator matrices R(X;T,V) in terms of growth conditions or of perturbations of R(0;T,V) = T ⊕ V.
Perturbations of Positive Semigroups and Applications to Population Genetics.