O спектре операторов в идеальных пространствах
Obere Schranken für Eigenwerte von Eigenwertaufgaben der Form (...2 I Â?...A Â? B) x = 0 . - Upper Bounds for Eigenvalues of Quadratic Eigenvalue Problem.
Observability properties of a semi-discrete 1d wave equation derived from a mixed finite element method on nonuniform meshes
The goal of this article is to analyze the observability properties for a space semi-discrete approximation scheme derived from a mixed finite element method of the 1d wave equation on nonuniform meshes. More precisely, we prove that observability properties hold uniformly with respect to the mesh-size under some assumptions, which, roughly, measures the lack of uniformity of the meshes, thus extending the work [Castro and Micu, Numer. Math.102 (2006) 413–462] to nonuniform meshes. Our results...
Odd anharmonic oscillators and shape resonances
Oka-analyticity of the essential spectrum
On a binary relation between normal operators
The main goal of this paper is to clarify the antisymmetric nature of a binary relation ≪ which is defined for normal operators A and B by: A ≪ B if there exists an operator T such that for all Borel subset Δ of the complex plane ℂ, where and are spectral measures of A and B, respectively (the operators A and B are allowed to act in different complex Hilbert spaces). It is proved that if A ≪ B and B ≪ A, then A and B are unitarily equivalent, which shows that the relation ≪ is a partial order...
On a certain algorithm of eigenvalue localization for normal operators
On a certain class of always convergent sequences and the Rayleigh quotient iterations
On a certain class of nonstationary sequences in Hilbert space.
On a class of -contractions: hyperinvariant subspaces and intertwining operators.
On a class of nonlinear eigenvalue problems
On a Class of Normaloid Operators.
On a class of operators
On a Class of Time Inhomogeneous Nonsingular Flows and Schrödinger Operators.
On a class of Toeplitz + Hankel operators.
On a completion of prehilbertian spaces.
On a -parameter ergodic theorem for continuous semigroups of operators satisfying norm conditions
A continuous multiparameter version of Chacon's vector valued ergodic theorem is proved.
On a decomposition for pairs of commuting contractions
A new decomposition of a pair of commuting, but not necessarily doubly commuting contractions is proposed. In the case of power partial isometries a more detailed decomposition is given.
On a Five-Diagonal Jacobi Matrices and Orthogonal Polynomials on Rays in the Complex Plane
∗ Partially supported by Grant MM-428/94 of MESC.Systems of orthogonal polynomials on the real line play an important role in the theory of special functions [1]. They find applications in numerous problems of mathematical physics and classical analysis. It is known, that classical polynomials have a number of properties, which uniquely define them.
On a fixed-point theorem of Cellina
In questa nota mostriamo come un teorema di esistenza per funzionali lineari porti un nuovo teorema di punto fisso che generalizza un teorema di punto fisso di Cellina.