On the similarity of boundary triples of symmetric operators in Krein spaces

Abstract

It is a classical result that the Weyl function of a simple symmetric operator in a Hilbert space determines a boundary triple uniquely up to unitary equivalence. We generalize this result to a simple symmetric operator in a Pontryagin space, where unitary equivalence is replaced by the similarity realized via a standard unitary operator.

Minor improvements, to appear in Complex. Anal. Oper. Theory