## p-robust multilevel algebraic error estimator & solver

Main results: multilevel a posteriori estimator of the algebraic error; guaranteed (reliable) and efficient; polynomial-degree robust; gives rise to a multilevel iterative algebraic solver with contraction independent of p; equivalence estimator – solver; Construction: global coarsest-level solve of lowest-order (p=1); local patchwise contributions from other levels; corresponds to V-cycle geometric…