Zsigmond Tarcsay

activity

20142026

most citedOperators having selfadjoint squares

8 citations · 17 across the 22 of their papers we have counts for

collaborators

31 papers

math.FA2026

Operators on anti-dual pairs: Means of positive operators

Zsigmond Tarcsay, Ábel Göde

We develop a theory of Kubo-Ando type means for positive operators on anti-dual pairs. This framework extends the classical theory of operator means beyond bounded Hilbert space op…

math.FA2025

Basic representation theorems of forms

Zoltán Sebestyén, Zsigmond Tarcsay

We study maximal representations of nonnegative sesquilinear forms in real or complex Hilbert spaces, that are not necessarily closed or even closable. We associate positive self-a…

hep-th2025

Existence theorem on the UV limit of Wilsonian RG flows of Feynman measures

Andras Laszlo, Zsigmond Tarcsay, Jobst Ziebell

In nonperturbative formulation of Euclidean signature quantum field theory (QFT), the vacuum state is characterized by the Wilsonian renormalization group (RG) flow of Feynman meas…

math.FA2024

Operators on anti-dual pairs: Lebesgue decomposition via Arlinskii's iteration

Ábel Göde, Zsigmond Tarcsay

The aim of this paper is to prove a general Lebesgue decomposition theorem for positive operators on so-called anti-dual pairs, following the iterative approach introduced by Arlin…

math.FA2023

Operators on anti-dual pairs: Supremum and infimum of positive operators

Zsigmond Tarcsay, Ábel Göde

Our purpose in this note is to investigate the order properties of positive operators from a locally convex space into its conjugate dual. We introduce a natural generalization of…

hep-th2023★ 1 cited

On the running and the UV limit of Wilsonian renormalization group flows

Andras Laszlo, Zsigmond Tarcsay

In nonperturbative formulation of quantum field theory (QFT), the vacuum state is characterized by the Wilsonian renormalization group (RG) flow of Feynman type field correlators.…

math.FA2022

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…

math.FA2021

Maps preserving the Douglas solution of operator equations

Zsigmond Tarcsay

We consider bijective maps $ϕ$ on the full operator algebra $B (H)$ of an infinite dimensional Hilbert space with the property that, for every $A,B,X\in \mathcal…

math.FA2020

Canonical graph contractions of linear relations on Hilbert spaces

Zsigmond Tarcsay, Zoltán Sebestyén

Given a closed linear relation $T$ between two Hilbert spaces $H$ and $K$ , the corresponding first and second coordinate projections $P_{T}$ and $Q_{T}$ are both line…

math.FA2020★ 2 cited

Perturbations of surjective homomorphisms between algebras of operators on Banach spaces

Bence Horváth, Zsigmond Tarcsay

A remarkable result of Molnár [Proc. Amer. Math. Soc., 126 (1998), 853-861] states that automorphisms of the algebra of operators acting on a separable Hilbert space is stable unde…

math.FA2020

Operators on anti-dual pairs: self-adjoint extensions and the Strong Parrott Theorem

Zsigmond Tarcsay, Tamás Titkos

The aim of this paper is to develop an approach to obtain self-adjoint extensions of symmetric operators acting on anti-dual pairs. The main advantage of such a result is that it c…

math.FA2020

Maps preserving absolute continuity and singularity of positive operators

György Pál Gehér, Zsigmond Tarcsay, Titkos Tamás

In this paper we consider the cone of all positive, bounded operators acting on an infinite dimensional, complex Hilbert space, and examine bijective maps that preserve absolute co…

math.FA2020

Operators on anti-dual pairs: Generalized Schur complement

Zsigmond Tarcsay, Tamás Titkos

The goal of this paper is to develop the theory of Schur complementation in the context of operators acting on anti-dual pairs. As a byproduct, we obtain a natural generalization o…

math.FA2020

Range-kernel characterizations of operators which are adjoint of each other

Zoltán Sebestyén, Zsigmond Tarcsay

We provide necessary and sufficient conditions for a pair $S, T$ of Hilbert space operators in order that they satisfy $S^{*} = T$ and $T^{*} = S$ . As a main result we establish an improvem…

math.FA2019

Operators on anti-dual pairs: Lebesgue decomposition of positive operators

Zsigmond Tarcsay

In this paper we introduce and study absolute continuity and singularity of positive operators acting on anti-dual pairs. We establish a general theorem that can be considered as a…

math.FA2019

On the Operator Equations $A^{n} = A^{*} A$

Souheyb Dehimi, Mohammed Hichem Mortad, Zsigmond Tarcsay

Let $n \in N$ and let $A$ be a closed linear operator (everywhere bounded or unbounded). In this paper, we study (among others) equations of the type $A^{*} A = A^{n}$ where $n\geq…

math.FA2018

Operators on anti-dual pairs: Generalized Krein--von Neumann extension

Zsigmond Tarcsay, Tamás Titkos

The main aim of this paper is to generalize the classical concept of positive operator, and to develop a general extension theory, which overcomes not only the lack of a Hilbert sp…

math.FA2017

Quasi-units as orthogonal projections

Zsigmond Tarcsay, Tamás Titkos

The notion of quasi-unit has been introduced by Yosida in unital Riesz spaces. Later on, a fruitful potential theoretic generalization was obtained by Arsove and Leutwiler. Due to…

math.FA2017

On the adjoint of Hilbert space operators

Zoltán Sebestyén, Zsigmond Tarcsay

In general, it is a non trivial task to determine the adjoint $S^{*}$ of an unbounded operator $S$ acting between two Hilbert spaces. We provide necessary and sufficient conditions f…

math.FA2017

A characterization of positive normal functionals on the full operator algebra

Zoltán Sebestyén, Zsigmond Tarcsay, Tamás Titkos

Using the recent theory of Krein--von Neumann extensions for positive functionals we present several simple criteria to decide whether a given positive functional on the full opera…

math.FA2016

On the order structure of representable functionals

Zsigmond Tarcsay, Tamás Titkos

The main purpose of this paper is to investigate some natural problems regarding the order structure of representable functionals on $^{*}$ -algebras. We describe the extreme points o…

math.FA2015

Adjoint of sums and products of operators in Hilbert spaces

Zoltán Sebestyén, Zsigmond Tarcsay

We provide sufficient and necessary conditions guaranteeing equations $(A + B)^{*} = A^{*} + B^{*}$ and $(A B)^{*} = B^{*} A^{*}$ concerning densely defined unbounded operators $A, B$ between Hilbert spa…

math.OA2015

On the uniqueness of the Lebesgue decomposition of normal states on $B (H)$

Zoltán Sebestyén, Zsigmond Tarcsay, Tamás Titkos

The non-commutative theory of the Lebesgue-type decomposition of positive functionals is originated with S. P. Gudder. Although H. Kosaki's counterexample shows that the decomposit…

math.FA2015

On the parallel sum of positive operators, forms, and functionals

Zsigmond Tarcsay

The parallel sum $A : B$ of two bounded positive linear operators $A, B$ on a Hilbert space $H$ is defined to be the positive operator having the quadratic form \begin{equation*} \inf…

Operators on anti-dual pairs: Means of positive operators

Basic representation theorems of forms

Existence theorem on the UV limit of Wilsonian RG flows of Feynman measures

Operators on anti-dual pairs: Lebesgue decomposition via Arlinskii's iteration

Operators on anti-dual pairs: Supremum and infimum of positive operators

On the running and the UV limit of Wilsonian renormalization group flows

Extensions of positive symmetric operators and Krein's uniqueness criteria

Maps preserving the Douglas solution of operator equations

Canonical graph contractions of linear relations on Hilbert spaces

Perturbations of surjective homomorphisms between algebras of operators on Banach spaces

Operators on anti-dual pairs: self-adjoint extensions and the Strong Parrott Theorem

Maps preserving absolute continuity and singularity of positive operators

Operators on anti-dual pairs: Generalized Schur complement

Range-kernel characterizations of operators which are adjoint of each other

Operators on anti-dual pairs: Lebesgue decomposition of positive operators

On the Operator Equations An=A∗A

Operators on anti-dual pairs: Generalized Krein--von Neumann extension

Quasi-units as orthogonal projections

On the adjoint of Hilbert space operators

A characterization of positive normal functionals on the full operator algebra

On the order structure of representable functionals

Adjoint of sums and products of operators in Hilbert spaces

On the uniqueness of the Lebesgue decomposition of normal states on B(H)

On the parallel sum of positive operators, forms, and functionals

On the Operator Equations $A^{n} = A^{*} A$

On the uniqueness of the Lebesgue decomposition of normal states on $B (H)$