On the Krein-Rechtman theorem in the presence of multiple points (Q2170525)

A Nevanlinna function is a function holomorphic on \(\mathbb{C}^+\) and taking its values in \(\overline{\mathbb{C}^+}\). The Nevanlinna-Pick interpolation problem (NPIP) requires to find necessary and sufficient conditions for the existence of a Nevanlinna function taking given values of \(\overline{\mathbb{C}^+}\) at given points of \(\mathbb{C}^+\). The Krein-Rekhtman theorem provides necessary and sufficient conditions for the solvability of the NPIP. The author extends the Krein-Rekhtman theorem to the case when there are multiple points.