Superconvergence analysis of the lowest order rectangular Raviart-Thomas element for semilinear parabolic equation

Abstract In this paper, based on the special property of the lowest order rectangular Raviart–Thomas element on the rectangulation and skillfully dealing with the nonlinear term, the superclose estimates for original and flux variables in L ∞ ( L 2 ) -norm are derived firstly for the semilinear parabolic equation with backward Euler discretization in temporal direction. Then, by using a simple and efficient interpolation postprocessing approach, the global superconvergence results are obtained. Finally, a numerical experiment is provided to confirm the correctness of the theoretical analysis.