eigenvalue problem

What Are The Eigenvalues And Eigenfunctions Of The Sturm-Liouville Problem? (p(x)y′)′ + (q(x) + λr(x))y = 0, a < x < b, (plus boundary conditions), is called an eigenfunction, and the corresponding value of λ is called its eigenvalue. The eigenvalues of a Sturm-Liouville problem are the values of λ for which nonzero solutions exist.