Normal extensions of a singular differential operator on the right semi-axis

In this work, based on the method of Everitt–Zettl and using the Calkin–Gorbachuk method, all normal extensions of the minimal operator generated by a linear singular formally normal differential-operator expression of the first order in Hilbert spaces of vector-functions on the right semi-axis in terms of boundary values are described. Furthermore, the structure of the spectrum of these extensions is investigated.