Zobrazeno 1 - 10
of 210
pro vyhledávání: '"STOCHEL, JAN"'
We prove that a CPD unilateral weighted shift $W_{\lambda}$ of type III is a quasi-affine transform of the operator $M_z$ of multiplication by the independent variable on the $L^2(\rho)$-closure of analytic complex polynomials on the complex plane, w
Externí odkaz:
http://arxiv.org/abs/2411.04911
Autor:
Pietrzycki, Paweł, Stochel, Jan
In this paper, we study hyperrigidity for $C^*$-algebras. The absence of the unit in hyperrigid set creates the possibility of the existence of $R$-dilations with non-isometric $R$. This gives rise to the study of when a hyperrigid set is annihilated
Externí odkaz:
http://arxiv.org/abs/2411.04860
The celebrated Bishop theorem states that an operator is subnormal if and only if it is the strong limit of a net (or a sequence) of normal operators. By the Agler-Stankus theorem, $2$-isometries behave similarly to subnormal operator in the sense th
Externí odkaz:
http://arxiv.org/abs/2406.00541
Autor:
Pietrzycki, Paweł, Stochel, Jan
In this paper, we study hyperrigidity for singly generated commutative unital $C^*$-algebras. We look at hyperrigidity from four different points of view. The first is via operator-moment characterizations of spectral measures, the subject intensivel
Externí odkaz:
http://arxiv.org/abs/2405.20814
This paper is concerned with the convergence of power sequences and stability of Hilbert space operators, where "convergence" and "stability" refer to weak, strong and norm topologies. It is proved that an operator has a convergent power sequence if
Externí odkaz:
http://arxiv.org/abs/2404.08473
Criteria for an algebraic operator $T$ on a complex Hilbert space $\mathcal{H}$ to be unitary are established. The main one is written in terms of the convergence of sequences of the form $\{\|T^nh\|\}_{n=0}^{\infty}$ with $h\in \mathcal{H}$. Related
Externí odkaz:
http://arxiv.org/abs/2404.08386
Autor:
Stochel, Jan, Stochel, Jerzy
In this paper we characterize hyperbolic cosine transforms of (positive) Borel measures $\nu$ in terms of exponential convexity (Bernstein's terminology). The case of compactly supported measures $\nu$ is also considered. All of this is then applied
Externí odkaz:
http://arxiv.org/abs/2306.14338
The B-operators (abbreviation for Brownian-type operators) are upper triangular 2x2 block matrix operators that satisfy certain algebraic constraints. The purpose of this paper is to characterize the weak, the strongand the uniform stability of B-ope
Externí odkaz:
http://arxiv.org/abs/2306.03036
In this paper, we study Brownian-type operators, which are upper triangular $2\times 2$ block matrix operators with entries satisfying some algebraic constraints. We establish a lifting theorem stating that any Brownian-type operator with subnormal $
Externí odkaz:
http://arxiv.org/abs/2304.07968
Autor:
Chavan, Sameer, Stochel, Jan
We study a class of left-invertible operators which we call weakly concave operators. It includes the class of concave operators and some subclasses of expansive strict $m$-isometries with $m > 2$. We prove a Wold-type decomposition for weakly concav
Externí odkaz:
http://arxiv.org/abs/2108.10228