Friedrichs and Kre\uın type extensions in terms of representing maps

Seppo Hassi, Henk de Snoo

A semibounded operator or relation $S$ in a Hilbert space with lower bound $m\in \mathbb{R}$ has a symmetric extension $S_{\rm f}=S {\, \widehat + \,} (\{0\} \times {\rm mul\,} S…