TY - GEN A1 - Kornhuber, Ralf A1 - Zou, Qingsong T1 - Efficient and Reliable Hierarchical Error Estimates for the Discretization Error of Elliptic Obstacle Problems N2 - We present and analyze novel hierarchical a posteriori error estimates for self-adjoint elliptic obstacle problems. Our approach differs from straightforward, but non-reliable estimators~\cite{RHWHoppe_RKornhuber_1994a} by an additional extra term accounting for the deviation of the discrete free boundary in the localization step. We prove efficiency and reliability on a saturation assumption and a regularity condition on the underlying grid. Heuristic arguments suggest that the extra term is of higher order and preserves full locality. Numerical computations confirm our theoretical findings. Y1 - 2008 UR - https://opus4.kobv.de/opus4-matheon/frontdoor/index/index/docId/527 UR - https://nbn-resolving.org/urn:nbn:de:0296-matheon-5278 ER -