On Hill's equation with a discontinuous coefficient.
On the basis properties of a spectral problem with a spectral parameter in a boundary condition.
On the basis property of the root functions of differential operators with matrix coefficients
We obtain asymptotic formulas for eigenvalues and eigenfunctions of the operator generated by a system of ordinary differential equations with summable coefficients and periodic or antiperiodic boundary conditions. Then using these asymptotic formulas, we find necessary and sufficient conditions on the coefficients for which the system of eigenfunctions and associated functions of the operator under consideration forms a Riesz basis.
On the differential operators with periodic matrix coefficients.
On the growth of the spectral measure.
On the solution of a differential equation occurring in the problem of heat convection in laminar flow through a tube with slip-flow.
On the spectrum of the operator which is a composition of integration and substitution
Let ϕ: [0,1] → [0,1] be a nondecreasing continuous function such that ϕ(x) > x for all x ∈ (0,1). Let the operator be defined on L₂[0,1]. We prove that has a finite number of nonzero eigenvalues if and only if ϕ(0) > 0 and ϕ(1-ε) = 1 for some 0 < ε < 1. Also, we show that the spectral trace of the operator always equals 1.