TY - JOUR AU - Sebestyén, Zoltán AU - Tarcsay, Zsigmond TI - Characterizations of essentially self-adjoint and skew-adjoint operators JF - STUDIA SCIENTIARUM MATHEMATICARUM HUNGARICA J2 - STUD SCI MATH HUNG VL - 52 PY - 2015 IS - 3 SP - 371 EP - 385 PG - 15 SN - 0081-6906 DO - 10.1556/012.2015.52.3.1300 UR - https://m2.mtmt.hu/api/publication/2969008 ID - 2969008 N1 - Cited By :8 Export Date: 7 September 2022 AB - 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. LA - English DB - MTMT ER - TY - JOUR AU - Sebestyén, Zoltán AU - Tarcsay, Zsigmond TI - CHARACTERIZATIONS OF SELFADJOINT OPERATORS JF - STUDIA SCIENTIARUM MATHEMATICARUM HUNGARICA J2 - STUD SCI MATH HUNG VL - 50 PY - 2013 IS - 4 SP - 423 EP - 435 PG - 13 SN - 0081-6906 DO - 10.1556/SScMath.50.2013.4.1252 UR - https://m2.mtmt.hu/api/publication/2541922 ID - 2541922 AB - 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. LA - English DB - MTMT ER - TY - JOUR AU - Sebestyén, Zoltán AU - Tarcsay, Zsigmond TI - T∗T always has a positive selfadjoint extension JF - ACTA MATHEMATICA HUNGARICA J2 - ACTA MATH HUNG VL - 135 PY - 2012 IS - 1-2 SP - 116 EP - 129 PG - 14 SN - 0236-5294 DO - 10.1007/s10474-011-0154-7 UR - https://m2.mtmt.hu/api/publication/2433949 ID - 2433949 LA - English DB - MTMT ER -