In 1910 Herman Weyl published one of the most widely quoted papers of the 20th century in Analysis, which initiated the study of singular Sturm-Liouville problems. The work on the foundations of Quantum Mechanics in the 1920s and 1930s, including the proof of the spectral theorem for unbounded self-adjoint operators in Hilbert space by von Neumann and Stone, provided some of the motivation for the study of differential operators in Hilbert space with particular emphasis on self-adjoint operators and their spectrum. Since then the topic developed in several directions and many results and...

This book provides a modern survey of some basic properties of Sturm-Liouville problems and to bring the reader to the forefront of knowledge of some areas of the theory. For example, some special Sturm-Liouville eigenvalue problems are equivalent to certain Jacobi and cyclic Jacobi matrix eigenvalue problems. A new approach to problems with periodic conditions is developed.