8 citations · 12 across the 4 of their papers we have counts for
6 papers · 1 filter
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…
m-isometric operators and their local properties
Z. J. Jablonski, I. B. Jung, J. Stochel
In this paper we give necessary and sufficient conditions for a bounded linear Hilbert space operator to be an -isometry for an unspecified written in terms of conditions th…
Subnormality of unbounded composition operators over one-circuit directed graphs: exotic examples
Piotr Budzynski, Zenon Jan Jablonski, Il Bong Jung +1
A recent example of a non-hyponormal injective composition operator in an -space generating Stieltjes moment sequences, invented by three of the present authors, was built ove…
Unbounded Subnormal Composition Operators in L2-Spaces
Piotr Budzynski, Zenon Jan Jablonski, Il Bong Jung +1
A criterion for subnormality of unbounded composition operators in L2-spaces, written in terms of measurable families of probability measures satisfying the so-called consistency c…
Unbounded subnormal weighted shifts on directed trees
Piotr Budzynski, Zenon Jan Jablonski, Il Bong Jung +1
A new method of verifying the subnormality of unbounded Hilbert space operators based on an approximation technique is proposed. Diverse sufficient conditions for subnormality of u…
A hyponormal weighted shift on a directed tree whose square has trivial domain
Z. J. Jablonski, I. B. Jung, J. Stochel
It is proved that, up to isomorphism, there are only two directed trees that admit a hyponormal weighted shift with nonzero weights whose square has trivial domain. These are preci…