@article{MTMT:2969008,
	title = {Characterizations of essentially self-adjoint and skew-adjoint operators},
	url = {https://m2.mtmt.hu/api/publication/2969008},
	author = {Sebestyén, Zoltán and Tarcsay, Zsigmond},
	doi = {10.1556/012.2015.52.3.1300},
	journal-iso = {STUD SCI MATH HUNG},
	journal = {STUDIA SCIENTIARUM MATHEMATICARUM HUNGARICA},
	volume = {52},
	unique-id = {2969008},
	issn = {0081-6906},
	abstract = {An extension of von Neumann's characterization of essentially selfadjoint operators is given among not necessarily densely defined symmetric operators which are assumed to be closable. Our arguments are of algebraic nature and follow the idea of [1]. © 2015 Akadémiai Kiadó, Budapest.},
	keywords = {Symmetric operators; Skewadjoint operators; Skew-symmetric operators; Essentially selfadjoint operators},
	year = {2015},
	eissn = {1588-2896},
	pages = {371-385},
	orcid-numbers = {Tarcsay, Zsigmond/0000-0001-8102-5055}
}

@article{MTMT:2541922,
	title = {CHARACTERIZATIONS OF SELFADJOINT OPERATORS},
	url = {https://m2.mtmt.hu/api/publication/2541922},
	author = {Sebestyén, Zoltán and Tarcsay, Zsigmond},
	doi = {10.1556/SScMath.50.2013.4.1252},
	journal-iso = {STUD SCI MATH HUNG},
	journal = {STUDIA SCIENTIARUM MATHEMATICARUM HUNGARICA},
	volume = {50},
	unique-id = {2541922},
	issn = {0081-6906},
	abstract = {The purpose of this paper is to revise von Neumann's characterizations of selfadjoint operators among symmetric ones. In fact, we do not assume that the underlying Hilbert space is complex, nor that the corresponding operator is densely defined, moreover, that it is closed. Following Arens, we employ algebraic arguments instead of the geometric approach of von Neumann using the Cayley transform.},
	keywords = {characterization; PERTURBATION; Positive operator; HILBERT-SPACE; selfadjoint operator; Symmetric operator},
	year = {2013},
	eissn = {1588-2896},
	pages = {423-435},
	orcid-numbers = {Tarcsay, Zsigmond/0000-0001-8102-5055}
}

@article{MTMT:2433949,
	title = {T∗T always has a positive selfadjoint extension},
	url = {https://m2.mtmt.hu/api/publication/2433949},
	author = {Sebestyén, Zoltán and Tarcsay, Zsigmond},
	doi = {10.1007/s10474-011-0154-7},
	journal-iso = {ACTA MATH HUNG},
	journal = {ACTA MATHEMATICA HUNGARICA},
	volume = {135},
	unique-id = {2433949},
	issn = {0236-5294},
	keywords = {Positive operator; selfadjoint operator; closable operator; operator extension; Krein-von Neumann extension; Friedrichs extension},
	year = {2012},
	eissn = {1588-2632},
	pages = {116-129},
	orcid-numbers = {Tarcsay, Zsigmond/0000-0001-8102-5055}
}