24 citations · 51 across the 17 of their papers we have counts for
4 papers · 1 filter
A non-hyponormal operator generating Stieltjes moment sequences
Z. J. Jablonski, I. B. Jung, J. Stochel
A linear operator in a complex Hilbert space $\hh$ for which the set $\dzn{S}$ of its -vectors is dense in $\hh$ and is a Stieltjes mom…
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…
Normal extensions escape from the class of weighted shifts on directed trees
Zenon Jan Jablonski, Il Bong Jung, Jan Stochel
A formally normal weighted shift on a directed tree is shown to be a bounded normal operator. The question of whether a normal extension of a subnormal weighted shift on a directed…