Nonselfadjoint correct restrictions and extensions with real spectrum

Subject Spectral theory
Title Nonselfadjoint correct restrictions and extensions with real spectrum
Author(s) B.N.Biyarov, M. Raikhan
Keywords Correct restriction, Correct extension, Riesz basis
Abstract In this work we obtain sufficient conditions for the reality of the spectrum of some correct restrictions and extensions of operators. It is shown, that the system of eigenvectors forms a Riesz basis in the case of discrete spectrum.