M. Langer,
Eigenvalues of a λ-rational Sturm–Liouville problem,
Math. Nachr. 210 (2000), 163–176
Abstract:
The Sturm–Liouville problem
y'' + (λ + q/(u – λ))y = 0,
y(0) = 0, y(1) = 0,
is considered, which depends rationally on the eigenvalue parameter.
Estimates for the eigenvalues and especially for the embedded eigenvalues are proved.
Moreover, conditions for the non-existence of embedded eigenvalues are given.
y(0) = 0, y(1) = 0,