69 citations · 110 across the 13 of their papers we have counts for
7 papers · 1 filter
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…
Isometries of Grassmann spaces, II
Gy. P. Gehér, P. Šemrl
Botelho, Jamison, and Molnár \cite{BJM}, and Geh\' er and Šemrl \cite{GeS} have recently described the general form of surjective isometries of Grassmann spaces of all projections…
Wigner's theorem on Grassmann spaces
György Pál Gehér
Wigner's celebrated theorem, which is particularly important in the mathematical foundations of quantum mechanics, states that every bijective transformation on the set of all rank…
Asymptotic behaviour of Hilbert space operators with applications
György Pál Gehér
This dissertation summarizes my investigations in operator theory during my PhD studies. The first chapter is an introduction to that field of operator theory which was developed b…
Maps on real Hilbert spaces preserving the area of parallelograms and a preserver problem on self-adjoint operators
György Pál Gehér
In this paper first we describe all (not necessarily linear or bijective) transformations on with which preserve the area of parallelograms spanned…
Maps on classes of Hilbert space operators preserving measure of commutativity
György Pál Gehér, Gergő Nagy
In this paper first we give a partial answer to a question of L. Molnár and W. Timmermann. Namely, we will describe those linear (not necessarily bijective) transformations on the…
Asymptotic Behaviour and Cyclic Properties of Weighted Shifts on Directed Trees
György Pál Gehér
In this paper we investigate a new class of operators called weighted shifts on directed trees introduced recently in [Z. J. Jablonski, I. B. Jung and J. Stochel, A Non-hyponormal…