# Analysis of two transmission eigenvalue problems with a coated boundary condition

## TL;DR

This paper studies two transmission eigenvalue problems related to media with coated boundaries, proving the existence of infinitely many eigenvalues, their dependence on parameters, and providing numerical examples for the scalar case.

## Contribution

It introduces new analysis for electromagnetic and scalar zero-index transmission eigenvalue problems with coated boundaries, including existence proofs and parameter dependence.

## Key findings

- Infinitely many real eigenvalues exist for the problems.
- Eigenvalues depend monotonically on refractive index and boundary parameter.
- Numerical examples illustrate the scalar zero-index eigenvalue problem.

## Abstract

In this paper, we investigate two transmission eigenvalue problems associated with the scattering of a media with a coated boundary. In recent years, there has been a lot of interest in studying these eigenvalue problems. It can be shown that the eigenvalues can be recovered from the scattering data and hold information about the material properties of the media one wishes to determine. Motivated by recent works we will study the electromagnetic transmission eigenvalue problem and scalar `zero-index' transmission eigenvalue problem for a media with a coated boundary. Existence of infinitely many real eigenvalues will be proven as well as showing that the eigenvalues depend monotonically on the refractive index and boundary parameter. Numerical examples in two spatial dimensions are presented for the scalar `zero-index' transmission eigenvalue problem. Also, in our investigation we prove that as the boundary parameter tends to zero and infinity we recover the classical eigenvalue problems.