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math.FA2026
Hyperpositive functions, sector bounded functions and a trace formula
Daniel Alpay, Izchak Lewkowicz
We study an indexed family of functions closely related to functions ana- lytic and with a real positive part in the right open half plane (the so-called positive functions) and to…
math.FA2026
Operator model and a trace formula for pairs of unitary operators
Daniel Alpay, Fabrizio Colombo, Izchak Lewkowicz +1
Using the theory of reproducing kernel Hilbert spaces introduced by L. de Branges and J. Rovnyak we prove a trace formula for pairs of operators in Hilbert space in terms of a Cara…