pencil of ordinary differential operators

Multiple Completeness of the Root Functions of the Pencils of Differential Operators with Constant Coefficients and Splitting Boundary Conditions

Authors: Rykhlov V. S.

In the space of square summable functions on the main segment [0,1], the class of polynomial pencils of ordinary differential operators of the n-th order is considered. The coefficients of the differential expression are assumed to be constants. The boundary conditions are assumed to be splitting and two-point at the ends 0 and 1 (l of boundary conditions is taken only at the point 0, and the remaining n − l is taken at the point 1). The differential expression and the boundary forms are assumed to be homogeneous, that is, they contain only main parts.

On Multiple Completeness of the Root Functions of the Pencils of Differential Operators with Constant Coefficients

Authors: Rykhlov V. S., Parfilova O. V.

A class of the pencils of ordinary differential operators of n-th order with constant coefficients is considered. The roots of the characteristic equation of the pencils from this class are supposed to lie on a straight line containing the origin, provided that one of the roots lies on one part from the origin, the rest lie on another part. The cases when the system of root functions is m-fold (3 ≤ m ≤ n − 1) complete in the space of square summable functions on main interval are described.

On Multiple Completeness of the Root Functions for a Class of the Pencils of Differential Operators

Authors: Rykhlov V. S.

A polinomial pencil of ordinary differential operators of n-th order generated by a homogeneous differential expression with constant coefficients and by two-point boundary conditions of a special structure with lcondition sinzero only (1 ≤ l ≤ n−1) isconsidered in the space L 2 [0,1]. The case is studied, when the roots of the characteristic equation lieonaray coming from theorigin. Asufficient condition of m-fold completeness of the system of root functions for m ≤ n−l inthe space L 2 [0,1] isfound. Anaccuracy of obtained result is shown.

Multiple Non-Completeness for the System of Eigenfunctions of a Class of the Pencils of Ordinary Differential Operators

Authors: Shigaeva O.

A class of the pencils of ordinary differential operators of n-th order with constant coefficients is considered. The roots of the characteristic equation of the pencils from this class is supposed to lie on a straight line coming through the origin. The main condition is such that the generating functions for the system of eigen- and associatedfunctionsarelinearcombinationsofexponentialfunctions.

On Multiple Completeness of the Root Functions of a Certain Class of Pencils of Differential Operators with Constant Coefficients

Authors: Rykhlov V. S., Blinkova O. V.

A polinomial pencil of ordinary differential operators of n-th order generated by a homogeneous differential expression with constant coefficients and by two-point boundary conditions of a special structure with l conditions in zero only (1 ≤ l ≤ n−1) is considered in the space L2[0,1]. The case is studied, when the roots of the characteristic equation lie on a ray coming from the origin.

On 2-fold completeness of the eigenfunctions for the strongly irregular quadratic pencil of differential operators of second order

Authors: Parfilova O. V.

 A class of strongly irregular pencils of ordinary differential operators of second order with constant coefficients is considered. The roots of the characteristic equation of the pencils from this class are supposed to lie on a straight line coming through the origin and on the both side of the origin. Exact interval on which the system of eigenfunctions is 2-fold complete in the space of square summable functions is finded.