In this article we will introduce and investigate some generalized Jacobi matrices. These matrices have three-diagonal block structure and they are Hermitian. We will give necessary and sufficient conditions for selfadjointness ...

We solve the inverse spectral problem for a class of Sturm - Liouville operators with singular nonlocal potentials and nonlocal boundary conditions.

We study a relation between brick n-tuples of subspaces of a finite dimensional linear space, and irreducible n-tuples of subspaces of a finite dimensional Hilbert (unitary) space such that a linear combination, with ...

We prove that −Δ+V has purely discrete spectrum if V ≥ 0 and, for all M, |{x | V (x)<M}| < ∞ and various extensions.