On the Basis Property of Systems of Root Functions of Regular Boundary Value Problems for the Sturm-Liouville Operator

摘要

The present paper deals with boundary eigenvalue problems for the nonself-adjoint Sturm-Liouville operator Lu = u" - q(x)u (1) denned on the interval (0,1), where q(x) is an arbitrary complex-valued function in the class L1(0,1). Our main goal is to study the basis properties of systems of root functions of the operator (1) with regular but not strengthened regular boundary conditions. The interest in this problem has been stimulated by the papers [1-3].