A Rellich type theorem for discrete Maxwell operators

We study the Rellich type theorem (RT) for the Maxwell operator $\hat H^D=\hat D\hat H_0$ on ${\bf Z}^3$ with constant anisotropic medium, i.e. the permittivity and permeability of which are non-scalar constant diagonal matrices. We also study the unique continuation theorem for the perturbed Maxwell operator $\hat H^{D_p}=\hat {D}_p\hat H_0$ on ${\bf Z}^3$ where the permittivity and permeability are locally perturbed from a constant matrix on a compact set in ${\bf Z}^3$. It then implies that, if $\hat H^D- \lambda$ satisfies (RT), then all distributions $\hat u$ in Besov space $\mathcal B_0^{\ast}({\bf Z}^3;{\bf C}^3)$ satisfying the equation $(\hat H^{D_p} - \lambda) \hat u = 0$ outside a compact set vanish near infinity.