On bare and semibare points for some classes of operators
On Erb's uncertainty principle
We improve a result of Erb, concerning an uncertainty principle for orthogonal polynomials. The proof uses numerical range and a decomposition of some multiplication operators as a difference of orthogonal projections.
On multiparameter spectral theory.
On proper boundary points of the spectrum and complemented eigenspaces.
On the abstract theorem of Picard.
On the joint numerical status and tensor products.
On the local spectral properties of weighted shift operators
We study the local spectral properties of both unilateral and bilateral weighted shift operators.
On the numerical range of operators on locally and on H-locally convex spaces
The spatial numerical range for a class of operators on locally convex space was studied by Giles, Joseph, Koehler and Sims in [3]. The purpose of this paper is to consider some additional properties of the numerical range on locally convex and especially on -locally convex spaces.
On the polynomial numerical hull of a normal matrix.
On upper and lower bounds of the numerical radius and an equality condition
We give an inequality relating the operator norm of T and the numerical radii of T and its Aluthge transform. It is a more precise estimate of the numerical radius than Kittaneh's result [Studia Math. 158 (2003)]. Then we obtain an equivalent condition for the numerical radius to be equal to half the operator norm.
Orbits in strips