Root System of a Perturbation of a Selfadjoint Operator with Discrete Spectrum

James Adduci, Boris Mityagin

We analyze the perturbations $T+B$ of a selfadjoint operator $T$ in a Hilbert space $H$ with discrete spectrum $\{t_k\}$, $T{\varphi }_k=t_k{\varphi }_k$, as an extension of our constructions i…