Boundary Conditions for Sturm-Liouville Equation with Transition Regions and Barriers or Wells
Open Access
- 1 January 2021
- journal article
- research article
- Published by Scientific Research Publishing, Inc. in Advances in Pure Mathematics
- Vol. 11 (04), 254-295
- https://doi.org/10.4236/apm.2021.114018
Abstract
By means of expansions of rapidly in infinity decreasing functions in delta functions and their derivatives, we derive generalized boundary conditions of the Sturm-Liouville equation for transitions and barriers or wells between two asymptotic potentials for which the solutions are supposed as known. We call such expansions “moment series” because the coefficients are determined by moments of the function. An infinite system of boundary conditions is obtained and it is shown how by truncation it can be reduced to approximations of a different order (explicitly made up to third order). Reflection and refraction problems are considered with such approximations and also discrete bound states possible in nonsymmetric and symmetric potential wells are dealt with. This is applicable for large wavelengths compared with characteristic lengths of potential changes. In Appendices we represent the corresponding foundations of Generalized functions and apply them to barriers and wells and to transition functions. The Sturm-Liouville equation is not only interesting because some important second-order differential equations can be reduced to it but also because it is easier to demonstrates some details of the derivations for this one-dimensional equation than for the full three-dimensional vectorial equations of electrodynamics of media. The article continues a paper that was made long ago.Keywords
This publication has 6 references indexed in Scilit:
- Theory of ReflectionPublished by Springer Science and Business Media LLC ,2016
- Grenzbedingungen der Elektrodynamik für Medien mit räumlicher Dispersion und ÜbergangsschichtenAnnalen der Physik, 1980
- Optical and Electrooptical Properties of the Interfaces of MediaPhysica Status Solidi (b), 1976
- A statistical theory of the dielectric properties of thin island films: I. The surface material coefficientsPhysica, 1974
- A phenomenological theory of the dielectric properties of thin filmsPhysica, 1973
- Recherches sur la théorie des QuantaAnnales de Physique, 1925