Article
Keywords:
semi-coercive elliptic problems; Poisson equation; finite elements; convergence; dual problem; a posteriori error estimates; variational inequalities
Summary:
The Poisson equation with non-homogeneous unilateral condition on the boundary is solved by means of finite elements. The primal variational problem is approximated on the basis of linear triangular elements, and $O(h)$-convergence is proved provided the exact solution is regular enough. For the dual problem piecewise linear divergence-free approximations are employed and $O(h^{3/2})$-convergence proved for a regular solution. Some a posteriori error estimates are also presented.
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