Pointwise Error Estimates for Differences in Piecewise Linear Finite Element Approximations

  • Authors:
  • Alfred H. Schatz;Lars B. Wahlbin

  • Affiliations:
  • -;-

  • Venue:
  • SIAM Journal on Numerical Analysis
  • Year:
  • 2003

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Abstract

We consider piecewise linear finite element approximations uh to u the solution of an elliptic boundary value problem. New estimates for the differences |e(x1)-e(x2)| (where e(x) = u(x)-u_h(x) is the error and x1 and x2 are any two points in the domain) are obtained in terms of weighted $L_\infty$ norms. As a consequence, so-called asymptotic expansion inequalities are derived that have been applied to obtain asymptotically exact a posteriori estimators for the gradient on each element.