Convergence and optimality of adaptive edge finite element methods for time-harmonic Maxwell equations

We consider a standard Adaptive Edge Finite Element Method (AEFEM) based on arbitrary order Nédélec edge elements, for three-dimensional indefinite time-harmonic Maxwell equations. We prove that the AEFEM gives a contraction for the sum of the energy error and the scaled error estimator, between two consecutive adaptive loops provided the initial mesh is fine enough. Using the geometric decay, we show that the AEFEM yields the best-possible decay rate of the error plus oscillation in terms of the number of degrees of freedom. The main technical contribution of the paper is in the establishment of a quasi-orthogonality and a localized a posteriori error estimator.