High-order nodal discontinuous Galerkin methods for the Maxwell eigenvalue problem

The Maxwell eigenvalue problem is known to pose difficulties for standard numerical methods, predominantly due to its large null space. As an alternative to the widespread use of Galerkin finite-element methods based on curl-conforming elements, we propose to use high-order nodal elements in a discontinuous element scheme. We consider both two- and three-dimensional problems and show the former to be without problems in a wide range of cases. Numerical experiments suggest the validity of this for general problems. For the three-dimensional eigenproblem, we encounter difficulties with a naive formulation of the scheme and propose minor modifications, intimately related to the discontinuous nature of the formulation, to overcome these concerns. We conclude by connecting the findings to time domain solution of Maxwell's equations. The discussion, analysis, and numerous computational experiments suggest that using discontinuous element schemes for solving Maxwell's equation in the frequency- or time-domain present a high-order accurate, efficient and robust alternative to classical Galerkin finite-element methods.