Kalenyuk P. I.
Spectral properties of nonself-adjoint nonlocal boundary-value problems for the operator of differentiation of even order
Ukr. Mat. Zh. - 2018. - 70, № 6. - pp. 739-751
We study spectral properties of an essentially nonself-adjoint problem generated by nonlocal multipoint conditions for the operator of differentiation of order 2n and analyze the cases of regular and irregular Birkhoff boundary conditions. A system of root functions of the problem and elements of biorthogonal systems are constructed. We also establish sufficient conditions under which these systems are complete and form a Riesz basis under certain additional assumptions.
Ukr. Mat. Zh. - 1992. - 44, № 9. - pp. 1201–1209
Necessary and sufficient conditions for the solvability of a bilinear matrix functional equation are presented. The conditions are applied in the construction of the solutions of systems of partial differential equations.
Ukr. Mat. Zh. - 1974. - 26, № 5. - pp. 652–657