Polynomially bounded operators.
Projectivity and lifting of Hilbert module maps
In a recent paper, Carlson, Foiaş, Williams and the author proved that isometric Hilbert modules are projective in the category of Hilbert modules similar to contractive ones. In this paper, a simple proof, based on a strengthened lifting theorem, is given. The proof also applies to an equivalent theorem of Foiaş and Williams on similarity to a contraction of a certain 2 × 2 operator matrix.
Quasi-constricted linear operators on Banach spaces
Let X be a Banach space over ℂ. The bounded linear operator T on X is called quasi-constricted if the subspace is closed and has finite codimension. We show that a power bounded linear operator T ∈ L(X) is quasi-constricted iff it has an attractor A with Hausdorff measure of noncompactness for some equivalent norm ||·||₁ on X. Moreover, we characterize the essential spectral radius of an arbitrary bounded operator T by quasi-constrictedness of scalar multiples of T. Finally, we prove that every...
Quelques propriétés des opérateurs uniformément convexifiants
Remarks on similarity and quasisimilarity of operators
Some locally mean ergodic theorems
The notion of local mean ergodicity is introduced. Some general locally mean ergodic theorems for linear and affine operators are presented. Locally mean ergodic theorems for affine operators whose linear parts are compact or similar to subnormal operators on a Hilbert space are given.
Some new classes of operators between Banach spaces. Semitauberian operators.
Spectral characterization of operators with precompact orbit
Spectral isometries
In this survey, we summarise some of the recent progress on the structure of spectral isometries between C*-algebras.
Spectral pictures of operators quasisimilar to the unilateral shift.
Stabilization of Timoshenko beam by means of pointwise controls
We intend to conduct a fairly complete study on Timoshenko beams with pointwise feedback controls and seek to obtain information about the eigenvalues, eigenfunctions, Riesz-Basis-Property, spectrum-determined-growth-condition, energy decay rate and various stabilities for the beams. One major difficulty of the present problem is the non-simplicity of the eigenvalues. In fact, we shall indicate in this paper situations where the multiplicity of the eigenvalues is at least two. We build all the above-mentioned...
Stabilization of Timoshenko Beam by Means of Pointwise Controls
We intend to conduct a fairly complete study on Timoshenko beams with pointwise feedback controls and seek to obtain information about the eigenvalues, eigenfunctions, Riesz-Basis-Property, spectrum-determined-growth-condition, energy decay rate and various stabilities for the beams. One major difficulty of the present problem is the non-simplicity of the eigenvalues. In fact, we shall indicate in this paper situations where the multiplicity of the eigenvalues is at least two. We build all the...
Structure of maximal spectral spaces of generalized scalar operators
Sums of square-zero operators
Supercyclicity and weighted shifts
An operator (linear and continuous) in a Fréchet space is hypercyclic if there exists a vector whose orbit under the operator is dense. If the scalar multiples of the elements in the orbit are dense, the operator is supercyclic. We give, for Fréchet space operators, a Supercyclicity Criterion reminiscent of the Hypercyclicity Criterion. We characterize the supercyclic bilateral weighted shifts in terms of their weight sequences. As a consequence, we show that a bilateral weighted shift is supercyclic...
Sur les opérateurs nilpotents d'ordre deux
The curvature function and similarity of operators
Towards a non-selfadjoint version of Kadison's theorem.
Über Endomorphismen mit dichten Bahnen.
Unitary parts of generalized Hankel operators