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For arbitrary closed countable subsets $Z$ of the unit circle examples of topologically mixing operators on Hilbert spaces are given which have a densely spanning set of unimodular eigenvectors with eigenvalues restricted to $Z$. In…

Dynamical Systems · Mathematics 2022-09-19 Hans-Peter Beise , Leonhard Frerick , Jürgen Müller

It is shown that, under some natural additional conditions, an operator which intertwines one cyclic singular unitary operator with one dimensional perturbation of another cyclic singular unitary operator is the operator of multiplication…

Functional Analysis · Mathematics 2020-05-11 Maria F. Gamal'

In this paper we give necessary and sufficient conditions for a bounded linear Hilbert space operator to be an $m$-isometry for an unspecified $m$ written in terms of conditions that are applied to "one vector at a time". We provide…

Functional Analysis · Mathematics 2019-06-13 Z. J. Jablonski , I. B. Jung , J. Stochel

We show that a diagonalizable (non-Hermitian) Hamiltonian H is pseudo-Hermitian if and only if it has an antilinear symmetry, i.e., a symmetry generated by an invertible antilinear operator. This implies that the eigenvalues of H are real…

Mathematical Physics · Physics 2015-06-26 Ali Mostafazadeh

Let X be a real Banach space. We prove that the existence of an injective, positive, symmetric and not strictly singular operator from X into its dual implies that either X admits an equivalent Hilbertian norm or it contains a nontrivially…

Functional Analysis · Mathematics 2008-06-02 D. Drivaliaris , N. Yannakakis

Finite rank perturbations of diagonalizable normal operators acting boundedly on infinite dimensional, separable, complex Hilbert spaces are considered from the standpoint of view of the existence of invariant subspaces. In particular, if…

Functional Analysis · Mathematics 2024-02-01 Eva A. Gallardo-Gutiérrez , F. Javier González-Doña

In this paper we consider a problem of the similarity of complex symmetric operators to perturbations of restrictions of normal operators. For a subclass of cyclic complex symmetric operators in a finite-dimensional Hilbert space we prove…

Functional Analysis · Mathematics 2021-06-29 Sergey M. Zagorodnyuk

The notion of B-convexity for operator spaces, which a priori depends on a set of parameters indexed by $\Sigma$, is defined. Some of the classical characterizations of this geometric notion for Banach spaces are studied in this new…

Operator Algebras · Mathematics 2007-05-23 Javier Parcet

In this work we consider hypercyclic operators as a special case of Polish dynamical systems. In the first section we analyze the construction of Bayart and Grivaux of a hypercyclic operator which preserves a Gaussian measure, and derive a…

Dynamical Systems · Mathematics 2020-10-07 Yiftach Dayan , Eli Glasner

In this paper we extend the notion of a locally hypercyclic operator to that of a locally hypercyclic tuple of operators. We then show that the class of hypercyclic tuples of operators forms a proper subclass to that of locally hypercyclic…

Functional Analysis · Mathematics 2009-10-02 G. Costakis , D. Hadjiloucas , A. Manoussos

We consider the Laplace-Beltrami operator in tubular neighbourhoods of curves on two-dimensional Riemannian manifolds, subject to non-Hermitian parity and time preserving boundary conditions. We are interested in the interplay between the…

Mathematical Physics · Physics 2015-05-18 David Krejcirik , Petr Siegl

We establish a spectral characterization theorem for the operators on complex Hilbert spaces of arbitrary dimensions that attain their norm on every closed subspace. The class of these operators is not closed under addition. Nevertheless,…

Functional Analysis · Mathematics 2016-07-13 Satish K. Pandey , Vern I. Paulsen

In this paper, we study the hypercyclic composition operators on weighted Banach spaces of functions defined on discrete metric spaces. We show that the only such composition operators act on the "little" spaces. We characterize the bounded…

Functional Analysis · Mathematics 2022-07-28 Robert F. Allen , Flavia Colonna , Rubén A. Martínez-Avendaño , Matthew A. Pons

In this paper we first introduce the extended limit set $J_{\{T^n\}}(x)$ for a sequence of bounded linear operators $\{T_n\}_{n=1}^{\infty}$ on a separable Banach space $X$ . Then we study the dynamics of sequence of linear operators by…

Functional Analysis · Mathematics 2017-03-10 M. R. Azimi

We show that the multiples of the backward shift operator on the spaces $\ell_{p}$, $1\leq p<\infty$, or $c_{0}$, when endowed with coordinatewise multiplication, do not possess frequently hypercyclic algebras. More generally, we…

Dynamical Systems · Mathematics 2019-04-04 Javier Falcó , Karl-G. Grosse-Erdmann

In this paper, a sufficient condition for the existence of hyperinvariant subspace of compact perturbations of multiplication operators on some Banach spaces is presented. An interpretation of this result for compact perturbations of normal…

Functional Analysis · Mathematics 2014-04-07 Hubert Klaja

We prove that a large class of trace-class perturbations of diagonalizable normal operators on a separable, infinite dimensional complex Hilbert space have non-trivial closed hyperinvariant subspaces. Moreover, a large subclass consists of…

Functional Analysis · Mathematics 2025-03-03 Eva A. Gallardo-Gutiérrez , F. Javier González-Doña

Let $H_1,H_2$ be complex Hilbert spaces and $T$ be a densely defined closed linear operator (not necessarily bounded). It is proved that for each $\epsilon>0$, there exists a bounded operator $S$ with $\|S\|\leq \epsilon$ such that $T+S$ is…

Functional Analysis · Mathematics 2016-09-23 S. H. Kulkarni , G. Ramesh

A linear operator $U$ acting boundedly on an infinite-dimensional separable complex Hilbert space $H$ is universal if every linear bounded operator acting on $H$ is similar to a scalar multiple of a restriction of $U$ to one of its…

Functional Analysis · Mathematics 2024-06-05 Luciano Abadías , F. Javier González-Doña , Jesús Oliva-Maza

The property of cyclicity of a linear operator, or equivalently the property of simplicity of its spectrum, is an important spectral characteristic that appears in many problems of functional analysis and applications to mathematical…

Mathematical Physics · Physics 2014-03-31 Evgeny Abakumov , Constanze Liaw , Alexei Poltoratski