Error estimates for some quasi-interpolation operators. (English) Zbl 0938.65125

Explicit bounds on the constants for two quasi-interpolation operators which are modifications of the classical Clément-operator is derived. The estimates proposed are crucial for the construction of explicit constants which appear in the commonly used a posteriori error estimates. The obtained results are also compared with corresponding estimates for the standard nodal interpolation operator.


65N15 Error bounds for boundary value problems involving PDEs
65N30 Finite element, Rayleigh-Ritz and Galerkin methods for boundary value problems involving PDEs
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