discipline 
Mathematics

subject 
Operator
extensions

lecturers 
Zoltán Sebestyén 
credits 
2 
period 
1., 2., 3., 4. 
curriculum 
Hilbert space operators defined only on a subspace
called after Halmos suboperators.
Characterization of subpositive suboperators
are the key result. Subsymmetric suboperators are given as a corollary. Krein’s theory of subsymmetric
contractions are generalised. Subsymmetric and
compact operator extension is a given as the arithmetic mean of the smallest
and largest normpreserving such extensions. Subsymmetric unitary operators are characterized as
symmetric isometries. Applications to dilation
theory are also given. 
literature 
 
form of tuition 
Lectures 
mode of assessment 
oral exam 