Eigenvalue approximation by a mixed method for resonant inhomogeneous cavities with metallic boundaries
Vincent Levillain · Mathematics of Computation · 1992
For an inhomogeneous cavity bounded by a perfect conductor, we prove that the approximation of the eigenvalues for the Maxwell problem leads to a second-order rate of convergence when using mixed finite elements. If the cavity has a disconnected boundary, the problem has null eigenvalues. We verify the existence of null eigenvalues for the approximate problem. They do not mix with the others that still converge at the same rate.