24 citations · 80 across the 39 of their papers we have counts for
41 papers · 1 filter
Solutions to the 'moment property implies subnormality' and injectivity problems for composition operators on one-circuit graphs
Piotr Budzyński, Zenon Jan Jabłoński, Il Bong Jung +1
We consider composition operators in , where is a discrete measure. Our main result shows that, for every integer , there exists a non-hyponormal composition ope…
CPD th roots of subnormal operators are subnormal
Zenon Jan Jabłoński, Il Bong Jung, Paweł Pietrzycki +1
We investigate the th root problem for bounded operators on a Hilbert space within the class of conditionally positive definite (CPD) operators determined by the Lévy--Khintchin…
When is a CPD weighted shift similar to a subnormal operator?
Zenon Jan Jabłoński, Il Bong Jung, Jan Stochel
We prove that a CPD unilateral weighted shift of type III is a quasi-affine transform of the operator of multiplication by the independent variable on the -clos…
Bishop-like theorems for non-subnormal operators
Zenon Jan Jabłoński, Il Bong Jung, Jan Stochel
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,…
Convergence of power sequences of operators via their stability
Zenon Jan Jabłoński, Il Bong Jung, Carlos Kubrusly +1
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 topolog…
Criteria for algebraic operators to be unitary
Zenon Jan Jablonski, Il Bong Jung, Jan Stochel
Criteria for an algebraic operator on a complex Hilbert space to be unitary are established. The main one is written in terms of the convergence of sequences of t…