The paper offers a self-consistent account of the spectral boundary value problems developed from the perspective of general theory of linear operators in Hilbert spaces. An abstract form of spectral boundary value problem with generalized boundary condition is introduced and results on its solvability complemented by representations of weak and strong solutions are obtained. The question of ex...

In this paper the spectral properties of Dirac operators Aη with electrostatic δ-shell interactions of constant strength η supported on compact smooth surfaces in R3 are studied. Making use of boundary triple techniques a Krein type resolvent formula and a Birman-Schwinger principle are obtained. With the help of these tools some spectral, scattering, and asymptotic properties of Aη are investi...

This paper discusses techniques for computing a few selected eigenvalue-eigenvector pairs of large and sparse symmetric matrices. A recently developed powerful class of techniques to solve this type of problems is based on integrating the matrix resolvent operator along a complex contour that encloses the interval containing the eigenvalues of interest. This paper considers such contour integra...

Abstract. We consider the approximation of semigroups e and of the functions φj(τA) that appear in exponential integrators by resolvent series. The interesting fact is that the resolvent series expresses the operator functions e and φj(τA), respectively, in efficiently computable terms. This is important for semigroups, where the new approximation is different from well-known approximations by ...

We investigate the generalized Drazin inverse and the generalized resolvent in Banach algebras. The Laurent expansion of the generalized resolvent in Banach algebras is introduced. The Drazin index of a Banach algebra element is characterized in terms of the existence of a particularly chosen limit process. As an application, the computing of the Moore-Penrose inverse in C∗-algebras is consider...

The coupled cluster method is applied to a strongly correlated lattice Hamiltonian, and the coupled cluster linear response method is extended to the calculation of electronic spectra by finding an approximation to a resolvent operator which describes the spectral response of the coupled cluster solution to excitation operators. In this spectral coupled cluster method, the ground and excited st...

We study the semiclassical estimates of the resolvent R(+ ii); 2 J R + ; 2]0;1] of a self-adjoint operator L(h) in the space of bounded operators L(H 0;s ; H 0;?s); s > 1=2. In the general case of long-range trapping "black-box" perturbations we prove that the estimate of the cut-oo resolvent k(x)R(+i0)(x)k H!H C exp(Ch ?p); (x) 2 C 1 0 (R n); p 1 implies the estimate kR(+ ii)k s;?s C 1 exp(C 1...