# Maximum norm a posteriori error estimates for convection–diffusion problems

We prove residual-type a posteriori error estimates in the maximum norm for a linear scalar elliptic convection–diffusion problem that may be singularly perturbed. Similar error analysis in the energy norm by Verfürth indicates that a dual norm of the convective derivative of the error must be added to the natural energy norm in order for the natural residual estimator to be reliable and efficient. We show that the situation is similar for the maximum norm. In particular, we define a mesh-dependent weighted seminorm of the convective error, which functions as a maximum-norm counterpart to the dual norm used in the energy norm setting. The total error is then defined as the sum of this seminorm, the maximum norm of the error and data oscillation. The natural maximum norm residual error estimator is shown to be equivalent to this total error notion, with constant independent of singular perturbation parameters. These estimates are proved under the assumption that certain natural estimates hold for the Green’s function for the problem at hand. Numerical experiments confirm that our estimators effectively capture the maximum-norm error behavior for singularly perturbed problems, and can effectively drive adaptive refinement in order to capture layer phenomena.

## Funding

### Topics in Mathematical Theory of Adaptive Finite Element Methods

Directorate for Mathematical & Physical Sciences

Find out more...### Finite Element Methods for the Surface Stokes Equation

Directorate for Mathematical & Physical Sciences

Find out more...### SFI Centre for Research Training in Foundations of Data Science

Science Foundation Ireland

Find out more...## History

## Publication

IMA Journal of Numerical Analysis, 2023, 43, 2562–2584## Publisher

Oxford Academic Press## Sustainable development goals

- (4) Quality Education

## External identifier

## Department or School

- Mathematics & Statistics