3 citations · 6 across the 7 of their papers we have counts for
7 papers
Extensions of positive symmetric operators and Krein's uniqueness criteria
Zoltán Sebestyén, Zsigmond Tarcsay
We revise Krein's extension theory of positive symmetric operators. Our approach using factorization through an auxiliary Hilbert space has several advantages: it can be applied to…
On the parallel sum of positive operators, forms, and functionals
Zsigmond Tarcsay
The parallel sum of two bounded positive linear operators on a Hilbert space is defined to be the positive operator having the quadratic form \begin{equation*} \inf…
On the sum between a closable operator and a -bounded operator
Dan Popovici, Zoltán Sebestyén, Zsigmond Tarcsay
We provide several perturbation theorems regarding closable operators on a real or complex Hilbert space. In particular we extend some classical results due to Hess--Kato, Kato--Re…
Extensions of positive operators and functionals
Zoltán Sebestyén, Zsolt Szűcs, Zsigmond Tarcsay
We consider linear operators defined on a subspace of a complex Banach space into its topological antidual acting positively in a natural sense. The goal of this paper is to invest…
A Short-type Decomposition Of Forms
Zoltán Sebestyén, Zsigmond Tarcsay, Tamás Titkos
The main purpose of this paper is to present a decomposition theorem for nonnegative sesquilinear forms. The key notion is the short of a form to a linear subspace. This is a gener…
Radon-Nikodym theorems for nonnegative forms, measures and representable functionals
Zsigmond Tarcsay
The aim of this note is to establish two Radon--Nikodym type theorems for nonnegative Hermitian forms defined on a real or complex vector space. We apply these results to prove the…