Selbstadjungierte Differentialoperatoren erster Ordnung in A2 (Co).
Selbstadjungierte Operatoren als ?dual" rein atomare Skalaroperatoren.
Self-adjoint differential vector-operators and matrix Hilbert spaces I
In the current work a generalization of the famous Weyl-Kodaira inversion formulas for the case of self-adjoint differential vector-operators is proved. A formula for spectral resolutions over an analytical defining set of solutions is discussed. The article is the first part of the planned two-part survey on the structural spectral theory of self-adjoint differential vector-operators in matrix Hilbert spaces.
Selfadjoint Means and Operator Monotone Functions.
Selfadjoint operator matrices with finite rows
A generalization of the Carleman criterion for selfadjointness of Jacobi matrices to the case of symmetric matrices with finite rows is established. In particular, a new proof of the Carleman criterion is found. An extension of Jørgensen's criterion for selfadjointness of symmetric operators with "almost invariant" subspaces is obtained. Some applications to hyponormal weighted shifts are given.
Semi-Browder operators and perturbations
An operator in a Banach space is called upper (resp. lower) semi-Browder if it is upper (lower) semi-Fredholm and has a finite ascent (resp. descent). An operator in a Banach space is called semi-Browder if it is upper semi-Browder or lower semi-Browder. We prove the stability of the semi-Browder operators under commuting Riesz operator perturbations. As a corollary we get some results of Grabiner [6], Kaashoek and Lay [8], Lay [11], Rakočević [15] and Schechter [16].
Semiclassical Analysis of the Largest Gap of Quasi-Periodic Schrödinger Operators
In this note, I wish to describe the first order semiclassical approximation to the spectrum of one frequency quasi-periodic operators. In the case of a sampling function with two critical points, the spectrum exhibits two gaps in the leading order approximation. Furthermore, I will give an example of a two frequency quasi-periodic operator, which has no gaps in the leading order of the semiclassical approximation.
Semiclassical Resonances and trace formulae for non-semi-bounded Hamiltonians
Semiclassical scattering by the Coulomb potential
Semi-Fredholm Maps of FK Spaces.
Semi-Fredholm operators and perturbations.
Semi-Fredholm operators and semigroups associated with some classical operator ideals
Semi-Fredholm Operators and Sequence Conditions.
Semi-groupes de contractions de classe de l’espace de Hilbert
Semigroups and resolvents of bounded variation, imaginary powers and H°° functional calculus.
Semigroups with nonquasianalytic growth
We study asymptotic behavior of -semigroups T(t), t ≥ 0, such that ∥T(t)∥ ≤ α(t), where α(t) is a nonquasianalytic weight function. In particular, we show that if σ(A) ∩ iℝ is countable and Pσ(A*) ∩ iℝ is empty, then , ∀x ∈ X. If, moreover, f is a function in which is of spectral synthesis in a corresponding algebra with respect to (iσ(A)) ∩ ℝ, then , where . Analogous results are obtained also for iterates of a single operator. The results are extensions of earlier results of Katznelson-Tzafriri,...
Sequences of differential operators: exponentials, hypercyclicity and equicontinuity
An eigenvalue criterion for hypercyclicity due to the first author is improved. As a consequence, some new sufficient conditions for a sequence of infinite order linear differential operators to be hypercyclic on the space of holomorphic functions on certain domains of are shown. Moreover, several necessary conditions are furnished. The equicontinuity of a family of operators as above is also studied, and it is characterized if the domain is . The results obtained extend or improve earlier work...
Sequential regularization of ill-posed problems involving unbounded operators
Sets with doubleton sections, good sets and ergodic theory
A Borel subset of the unit square whose vertical and horizontal sections are two-point sets admits a natural group action. We exploit this to discuss some questions about Borel subsets of the unit square on which every function is a sum of functions of the coordinates. Connection with probability measures with prescribed marginals and some function algebra questions is discussed.
Several variable spectral theory in the noncommutative case