Non-real eigenvalues of indefinite Sturm–Liouville problems

The present paper deals with non-real eigenvalues of regular indefinite Sturm–Liouville problems. A priori bounds and sufficient conditions of the existence for non-real eigenvalues are obtained under mild integrable conditions of coefficients.     

Spectral corrections for Sturm–Liouville problems

The numerical solution of the Sturm–Liouville problem can be achieved using shooting to obtain an eigenvalue approximation as a solution of a suitable nonlinear equation and then computing the corresponding eigenfunction. In this paper we use the shooting method both for eigenvalues and eigenfunctions. In integrating the corresponding initial value problems we resort to the boundary value method. The technique proposed seems to be well suited to supplying a general formula for the global discretization error of the eigenfunctions depending on the discretization errors arising from the numerical integration of the initial value problems. A technique to estimate the eigenvalue errors is also suggested, and seems to be particularly effective for the higher-index eigenvalues. Numerical experiments on some classical Sturm–Liouville problems are presented.     

Computing eigenvalues of Sturm–Liouville problems by Hermite interpolations

We establish a new method to compute the eigenvalues of Sturm?CLiouville problems by the use of Hermite interpolations at equidistant nodes. We rigorously give estimates for the error by considering both truncation and amplitude errors. We compare the results of the new technique with those involving the classical sinc method as well as a SLEIGN2-based method. We also introduce curves that illustrate the enclosure intervals.     

A symmetric generalization of Sturm–Liouville problems in discrete spaces

Classical Sturm–Liouville problems of a discrete variable are extended for symmetric functions such that the corresponding solutions preserve the orthogonality property. Some generic illustrative examples are given in this sense.     

Inequalities among eigenvalues of Sturm–Liouville problems with distribution potentials

This paper deals with the eigenvalue problems for the Sturm–Liouville operators generated by the differential expression

L(y)=−(p(x)y^′)^′+q(x)y$L\left(y\right)=-{\left(p\left(x\right)y^{\prime }\right)}^{\prime }+q\left(x\right)y$

with singular coefficients q(x)$q\left(x\right)$ in the sense of distributions. We obtain the inequalities among the eigenvalues corresponding to different self-adjoint boundary conditions. The continuity region, the differentiability and the monotonicity of the n$n$th eigenvalue corresponding to the separated boundary conditions are given. Oscillation properties of the eigenfunctions of all the coupled Sturm–Liouville problems are characterized. The main results of this paper can also be applied to solve a class of transmission problems.     

An Open Problem: Accumulation of Nonreal Eigenvalues of Indefinite Sturm–Liouville Operators

In this note we conjecture that the eigenvalues of singular indefinite Sturm–Liouville operators accumulate to the real axis whenever the eigenvalues of the corresponding definite Sturm–Liouville operator accumulate to the bottom of the essential spectrum from below.     

Matrix representations of Sturm–Liouville problems with eigenparameter-dependent boundary conditions

We show that a class of regular self-adjoint Sturm–Liouville problems with eigenparameter-dependent boundary conditions are equivalent to a certain class of matrix problems. Equivalent here means that they have exactly the same eigenvalues.     

On the Estimates of Periodic Eigenvalues of Sturm–Liouville Operators with Trigonometric Polynomial Potentials

Mathematical Notes - We provide estimates for the eigenvalues of non-self-adjoint Sturm–Liouville operators with periodic and antiperiodic boundary conditions for special potentials that are...     

On a class of singular Sturm–Liouville periodic boundary value problems

Keeping in mind the singular model for the periodic oscillations of the axis of a satellite in the plane of the elliptic orbit around its center of mass, we give sufficient conditions for the solvability of a class of singular Sturm–Liouville equations with periodic boundary value conditions. To this end, under a suitable change of variables, we present a new existence result for problems defined in the real half-line.     

New characterizations of spectral density functions for singular Sturm–Liouville problems

A generalization is given for a characterization of the spectral density function of Weyl and Titchmarsh for a singular Sturm–Liouville problem having absolutely continuous spectrum in [0,∞)$[0,\infty )$. A recurrent formulation is derived that generates a family of approximations based on this scheme. Proofs of convergence for these new approximations are supplied and a numerical method is implemented. The computational results show more rapid rates of convergence which are in accord with the theoretical rates.     

From Sturm–Liouville problems to fractional and anomalous diffusions

Some fractional and anomalous diffusions are driven by equations involving fractional derivatives in both time and space. Such diffusions are processes with randomly varying times. In representing the solutions to those equations, the explicit laws of certain stable processes turn out to be fundamental. This paper directs one’s efforts towards the explicit representation of solutions to fractional and anomalous diffusions related to Sturm–Liouville problems of fractional order associated to fractional power function spaces. Furthermore, we study a new version of Bochner’s subordination rule and we establish some connections between subordination and space-fractional operators.     

Nonlinear discrete Sturm–Liouville problems with global boundary conditions

This paper is devoted to the study of nonlinear difference equations subject to global nonlinear boundary conditions. We provide sufficient conditions for the existence of solutions based on properties of the nonlinearities and the eigenvalues of an associated linear Sturm–Liouville problem.