Robust a posteriori error estimators for a singularly perturbed reaction-diffusion equation (Q1377026)

The author obtains some robust a posteriori error estimators for a singularly perturbed boundary value problem attached to a linear reaction-diffusion equation. The term `robust' is used in the sense that the estimators furnish global upper and local lower bounds in the energy norm, such that the ratio of these bounds is itself bounded from below and above by constants that do neither depend on the meshsize, nor upon the perturbation parameter.