TY  - JOUR
AU  - Sebestyén, Zoltán
AU  - Stochel, J
TI  - On suboperators with codimension one domains
JF  - JOURNAL OF MATHEMATICAL ANALYSIS AND APPLICATIONS
J2  - J MATH ANAL APPL
VL  - 360
PY  - 2009
IS  - 2
SP  - 391
EP  - 397
PG  - 7
SN  - 0022-247X
DO  - 10.1016/j.jmaa.2009.06.062
UR  - https://m2.mtmt.hu/api/publication/2406325
ID  - 2406325
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Sebestyén, Zoltán
AU  - Stochel, J
TI  - On products of unbounded operators
JF  - ACTA MATHEMATICA HUNGARICA
J2  - ACTA MATH HUNG
VL  - 100
PY  - 2003
IS  - 1-2
SP  - 105
EP  - 129
PG  - 25
SN  - 0236-5294
DO  - 10.1023/A:1024660318703
UR  - https://m2.mtmt.hu/api/publication/2385743
ID  - 2385743
AB  - A symmetric operator X̂ is attached to each operator X that leaves the domain of a given positive operator A invariant and makes the product AX symmetric. Some spectral properties of X̂ are derived from those of X and, as a consequence, various conditions ensuring positivity of products of the form AX1 ⋯ Xn are proved. The question of Ω-complete positivity of the mapping p → Ap(X1, . . . , Xn) defined on complex polynomials in n variables is investigated. It is shown that the set Ω is related to the MCIntosh-Pryde joint spectrum of (X1, . . . , Xn) in case all the operators A, X1, . . . , Xn are bounded. Examples illustrating the theme of the paper are included.
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Sikolya, Eszter
AU  - Sebestyén, Zoltán
TI  - On Krein-von Neumann and Friedrichs extensions
JF  - ACTA SCIENTIARUM MATHEMATICARUM (SZEGED)
J2  - ACTA SCI MATH (SZEGED)
VL  - 69
PY  - 2003
SP  - 323
EP  - 336
PG  - 14
SN  - 0001-6969
UR  - https://m2.mtmt.hu/api/publication/1340569
ID  - 1340569
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Prokaj, Vilmos
AU  - Sebestyén, Zoltán
TI  - On extremal positive operator extensions
JF  - ACTA SCIENTIARUM MATHEMATICARUM (SZEGED)
J2  - ACTA SCI MATH (SZEGED)
VL  - 62
PY  - 1996
IS  - 3-4
SP  - 485
EP  - 491
PG  - 7
SN  - 0001-6969
UR  - https://m2.mtmt.hu/api/publication/1839283
ID  - 1839283
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Prokaj, Vilmos
AU  - Sebestyén, Zoltán
TI  - On Friedrichs extensions of operators
JF  - ACTA SCIENTIARUM MATHEMATICARUM (SZEGED)
J2  - ACTA SCI MATH (SZEGED)
VL  - 62
PY  - 1996
IS  - 1-2
SP  - 243
EP  - 246
PG  - 4
SN  - 0001-6969
UR  - https://m2.mtmt.hu/api/publication/1839282
ID  - 1839282
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Sebestyén, Zoltán
TI  - Operator extensions on Hilbert space
JF  - ACTA SCIENTIARUM MATHEMATICARUM (SZEGED)
J2  - ACTA SCI MATH (SZEGED)
VL  - 57
PY  - 1993
IS  - 1-4
SP  - 233
EP  - 248
PG  - 16
SN  - 0001-6969
UR  - https://m2.mtmt.hu/api/publication/3079731
ID  - 3079731
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Sebestyén, Zoltán
AU  - Stochel, Jan
TI  - Restrictions of positive selfadjoint operators
JF  - ACTA SCIENTIARUM MATHEMATICARUM (SZEGED)
J2  - ACTA SCI MATH (SZEGED)
VL  - 55
PY  - 1991
IS  - 1-2
SP  - 149
EP  - 154
PG  - 6
SN  - 0001-6969
UR  - https://m2.mtmt.hu/api/publication/3079745
ID  - 3079745
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Sebestyén, Zoltán
TI  - ON RANGES OF ADJOINT OPERATORS IN HILBERT-SPACE
JF  - ACTA SCIENTIARUM MATHEMATICARUM (SZEGED)
J2  - ACTA SCI MATH (SZEGED)
VL  - 46
PY  - 1983
IS  - 1-4
SP  - 295
EP  - 298
PG  - 4
SN  - 0001-6969
UR  - https://m2.mtmt.hu/api/publication/3066108
ID  - 3066108
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Sebestyén, Zoltán
TI  - RESTRICTIONS OF POSITIVE OPERATORS
JF  - ACTA SCIENTIARUM MATHEMATICARUM (SZEGED)
J2  - ACTA SCI MATH (SZEGED)
VL  - 46
PY  - 1983
IS  - 1-4
SP  - 299
EP  - 301
PG  - 3
SN  - 0001-6969
UR  - https://m2.mtmt.hu/api/publication/3066109
ID  - 3066109
LA  - English
DB  - MTMT
ER  -