A note on the almost left and almost right joint spectra of R. Harte
A note on the powers of Cesàro bounded operators
In this note we give a negative answer to Zem�nek’s question (1994) of whether it always holds that a Cesàro bounded operator on a Hilbert space with a single spectrum satisfies
A note on the stability of linear combinations of algebraic operators.
A numerical radius inequality involving the generalized Aluthge transform
A spectral radius inequality is given. An application of this inequality to prove a numerical radius inequality that involves the generalized Aluthge transform is also provided. Our results improve earlier results by Kittaneh and Yamazaki.
A Perturbation Theorem for the Essential Spectral Radius of Strongly Continuous Semigroups.
A product integral representation of the generalized inverse
A quasinilpotent operator with reflexive commutant
An example of a nonzero quasinilpotent operator with reflexive commutant is presented.
A quasi-nilpotent operator with reflexive commutant, II
A new example of a non-zero quasi-nilpotent operator T with reflexive commutant is presented. The norms converge to zero arbitrarily fast.
A remark on the d-characteristic and the -characteristic of linear operators in a Banach space
A resolvent condition implying power boundedness
The Ritt and Kreiss resolvent conditions are related to the behaviour of the powers and their various means. In particular, it is shown that the Ritt condition implies the power boundedness. This improves the Nevanlinna characterization of the sublinear decay of the differences of the consecutive powers in the Esterle-Katznelson-Tzafriri theorem, and actually characterizes the analytic Ritt condition by two geometric properties of the powers.
A Short Proof of Radjavi's Theorem on Self-Commutators.
A Short Proof of the Ando-Krieger Theorem.
A Spectral Gap Theorem for Dirac Operators with Central Field.
A spectral mapping theorem for Banach modules
Let G be a locally compact abelian group, M(G) the convolution measure algebra, and X a Banach M(G)-module under the module multiplication μ ∘ x, μ ∈ M(G), x ∈ X. We show that if X is an essential L¹(G)-module, then for each measure μ in reg(M(G)), where denotes the operator in B(X) defined by , σ(·) the usual spectrum in B(X), sp(X) the hull in L¹(G) of the ideal , μ̂ the Fourier-Stieltjes transform of μ, and reg(M(G)) the largest closed regular subalgebra of M(G); reg(M(G)) contains all...
A spectral mapping theorem for functions with finite Dirichlet integral.
A Spectral Mapping Theorem for Holomorphic Functions.
A Spectral Mapping Theorem for Local Multipliers.
A spectral mapping theorem for perturbed strongly continuous semigroups.
A spectral perturbation problem and its applications to waves above an underwater ridge.
A spectral theory for locally compact abelian groups of automorphisms of commutative Banach algebras
Let A be a commutative Banach algebra with Gelfand space ∆ (A). Denote by Aut (A) the group of all continuous automorphisms of A. Consider a σ(A,∆(A))-continuous group representation α:G → Aut(A) of a locally compact abelian group G by automorphisms of A. For each a ∈ A and φ ∈ ∆(A), the function t ∈ G is in the space C(G) of all continuous and bounded functions on G. The weak-star spectrum is defined as a closed subset of the dual group Ĝ of G. For φ ∈ ∆(A) we define to be the union of all...