On the Riesz Basisness of Systems Composed of Root Functions of Periodic Boundary Value Problems

الملخص EN

We consider the nonself-adjoint Sturm-Liouville operator with q ∈ L 1 [ 0,1 ] and either periodic or antiperiodic boundary conditions.

We obtain necessary and sufficient conditions for systems of root functions of these operators to be a Riesz basis in L 2 [ 0,1 ] in terms of the Fourier coefficients of q .