Boundary Recovery of Anisotropic Electromagnetic Parameters for the Time Harmonic Maxwell's Equations

Abstract

This work concerns inverse boundary value problems for the time-harmonic Maxwell's equations on differential $1-$forms. We formulate the boundary value problem on a $3-$dimensional compact and simply connected Riemannian manifold $M$ with boundary $\partial M$ endowed with a Riemannian metric $g$. Assuming that the electric permittivity $\varepsilon$ and magnetic permeability $\mu$ are real-valued anisotropic (i.e $(1,1)-$ tensors), we aim to determine certain metrics induced by these parameters, denoted by $\hat{\varepsilon}$ and $\hat{\mu}$ at $\partial M$. We show that the knowledge of the impedance and admittance maps determines the tangential entries of $\hat{\varepsilon}$ and $\hat{\mu}$ at $\partial M$ in their boundary normal coordinates, although the background volume form cannot be determined in such coordinates due to a non-uniqueness occuring from diffeomorphisms that fix the boundary. Then, we prove that in some cases, we can also recover the normal components of $\hat{\mu}$ up to a conformal multiple at $\partial M$ in boundary normal coordinates for $\hat{\varepsilon}$. Last, we build an inductive proof to show that if $\hat{\varepsilon}$ and $\hat{\mu}$ are determined at $\partial M$ in boundary normal coordinates for $\hat{\varepsilon}$, then the same follows for their normal derivatives of all orders at $\partial M$.