The spectral analysis of differential operators, Dissipative operators, Methods of the spectral analysis, Lax-Phillips scattering theory, Sz.-Nagy-Foiaş characteristic function theory, Methods of functional models, Nonlinear differential equations, Multiparameter spectral theory, Dynamical systems on time scales, Extension theory, Theory of deficiency indices, Weyl theory, Hamiltonian systems, Sturm-Liouville equations with distributional potentials, s-numbers, Trace class operators, Hilbert-Schmidt operators, Fractional analysis
