Optimal isoparametric finite elements and error estimates for domains involving curved boundaries
SIAM Journal on Numerical Analysis
Finite Element Method for Elliptic Problems
Finite Element Method for Elliptic Problems
The Immersed Interface Method: Numerical Solutions of PDEs Involving Interfaces and Irregular Domains (Frontiers in Applied Mathematics)
Journal of Computational Physics
Wavenumber-Explicit $hp$-BEM for High Frequency Scattering
SIAM Journal on Numerical Analysis
Journal of Scientific Computing
Journal of Computational and Applied Mathematics
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We analyze higher order finite elements applied to second order elliptic interface problems. Our a priori error estimates in the L^2- and H^1-norm are expressed in terms of the approximation order p and a parameter @d that quantifies how well the interface is resolved by the finite element mesh. The optimal p-th order convergence in the H^1(@W)-norm is only achieved under stringent assumptions on @d, namely, @d=O(h^2^p). Under weaker conditions on @d, optimal a priori estimates can be established in the L^2- and in the H^1(@W"@d)-norm, where @W"@d is a subdomain that excludes a tubular neighborhood of the interface of width O(@d). In particular, if the interface is approximated by an interpolation spline of order p and if full regularity is assumed, then optimal convergence orders p+1 and p for the approximation in the L^2(@W)- and the H^1(@W"@d)-norm can be expected but not order p for the approximation in the H^1(@W)-norm. Numerical examples in 2D and 3D illustrate and confirm our theoretical results.