Quasi-norm local error estimators for p-Laplacian

In this paper, we extend the quasi-norm techniques used in a priori error e stimation of finite element approximation of degenerate nonlinear systems i n order to carry out an improved a posteriori error analysis for the p-Lapl acian. We derive quasi-norm a posteriori error estimators of residual type, which are shown to provide improved upper and lower bounds on the discreti zation error. For sufficiently regular solutions, these estimators are furt her shown to be equivalent on the discretization error in a quasi norm. Num erical results demonstrating these a posteriori estimators are also present ed.