Mixing operators with prescribed unimodular eigenvalues

2020 ◽  
pp. 1-8
Author(s):  
H.-P. BEISE ◽  
L. FRERICK ◽  
J. MÜLLER
Keyword(s):  
Unit Circle ◽  
Hilbert Spaces ◽  
Mixing Operators ◽  
Spanning Set ◽  
Topologically Mixing

Abstract 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 eigenvectors with unimodular eigenvalues restricted to Z. In particular, these operators cannot be ergodic in the Gaussian sense.

scholarly journals The spectra of compact operators in Hilbert spaces

1965 ◽  
Vol 7 (1) ◽  
pp. 34-38
Author(s):  
T. T. West
Keyword(s):  
Hilbert Space ◽  
Unit Circle ◽  
Real Axis ◽  
Complex Plane ◽  
Hilbert Spaces ◽  
Compact Operators ◽  
Conformal Mappings ◽  
The Real ◽  
Finite Set

In [2] a condition, originally due to Olagunju, was given for the spectra of certain compact operators to be on the real axis of the complex plane. Here, by using conformal mappings, this result is extended to more general curves. The problem divides naturally into two cases depending on whether or not the curve under consideration passes through the origin. Discussion is confined to the prototype curves C0 and C1. The case of C0, the unit circle of centre the origin, is considered in § 3; this problem is a simple one as the spectrum is a finite set. In § 4 results are given for C1 the unit circle of centre the point 1, and some results on ideals of compact operators, given in § 2, are needed. No attempt has been made to state results in complete generality (see [2]); this paper is kept within the framework of Hilbert space, and particularly simple conditions may be given if the operators are normal.

Trapezoid type inequalities for complex functions defined on the unit circle with applications for unitary operators in Hilbert spaces

2016 ◽  
Vol 23 (2) ◽  
Author(s):  
Sever S. Dragomir
Keyword(s):  
Unit Circle ◽  
Hilbert Spaces ◽  
Stieltjes Integral ◽  
Unitary Operators ◽  
Complex Functions ◽  
Continuous Complex ◽  
Complex Valued

AbstractSome trapezoid type inequalities for the Riemann–Stieltjes integral of continuous complex-valued integrands defined on the complex unit circle

scholarly journals Grüss Type Inequalities for Complex Functions Defined on Unit Circle with Applications for Unitary Operators in Hilbert Spaces

2015 ◽  
Vol 49 (1) ◽  
pp. 77-94 ◽  
Author(s):  
Silvestru Sever Dragomir
Keyword(s):  
Unit Circle ◽  
Hilbert Spaces ◽  
Unitary Operators ◽  
Complex Functions ◽  
Grüss Type Inequalities

Se proporcionan algunas desigualdades tipo Grüss para la integral de Riemann-Stieltjes de integrandos de valores continuos complejos definidos sobre el circulo unitario complejo C(0, 1) y varias subclases de integradores son dados. Aplicaciones naturales para funciones de operadores unitarios en espacios de Hilbert son proporcionadas.

scholarly journals Finite-part singular integral approximations in Hilbert spaces

2004 ◽  
Vol 2004 (52) ◽  
pp. 2787-2793
Author(s):  
E. G. Ladopoulos ◽  
G. Tsamasphyros ◽  
V. A. Zisis
Keyword(s):  
Unit Circle ◽  
Integral Equations ◽  
Singular Integral ◽  
Hilbert Spaces ◽  
Existence Theorems ◽  
Singular Integral Equations ◽  
Finite Part ◽  
Algebraic Equations ◽  
Integration Interval ◽  
Linear Algebraic Equations

Some new approximation methods are proposed for the numerical evaluation of the finite-part singular integral equations defined on Hilbert spaces when their singularity consists of a homeomorphism of the integration interval, which is a unit circle, on itself. Therefore, some existence theorems are proved for the solutions of the finite-part singular integral equations, approximated by several systems of linear algebraic equations. The method is further extended for the proof of the existence of solutions for systems of finite-part singular integral equations defined on Hilbert spaces, when their singularity consists of a system of diffeomorphisms of the integration interval, which is a unit circle, on itself.

scholarly journals $k$-bitransitive and compound operators on Banach spaces

2016 ◽  
Vol 8 (1) ◽  
pp. 3-10
Author(s):  
N. Bamerni ◽  
A. Kilicman
Keyword(s):  
Banach Spaces ◽  
Sufficient Conditions ◽  
Direct Sum ◽  
Mixing Operators ◽  
Topologically Mixing ◽  
Compound Operators

In this this paper, we introduce new classes of operators in complex Banach spaces, which we call $k$-bitransitive operators and compound operators to study the direct sum of diskcyclic operators. We create a set of sufficient conditions for an operator to be $k$-bitransitive or compound. We give a relation between topologically mixing operators and compound operators. Also, we extend the Godefroy-Shapiro Criterion for topologically mixing operators to compound operators.

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