Karkulik, M., Melenk, J. M., & Rieder, A. (2023). On interpolation spaces of piecewise polynomials on mixed meshes. arXiv. https://doi.org/10.48550/arXiv.2306.16907
We consider fractional Sobolev spaces Hθ, θ∈(0,1), on 2D domains and H1-conforming discretizations by globally continuous piecewise polynomials on a mesh consisting of shape-regular triangles and quadrilaterals. We prove that the norm obtained from interpolating between the discrete space equipped with the L2-norm on the one hand and the H1-norm on the other hand is equivalent to the corresponding continuous interpolation Sobolev norm, and the norm-equivalence constants are independent of meshsize and polynomial degree. This characterization of the Sobolev norm is then used to show an inverse inequality between H1 and Hθ.
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Mathematical and Algorithmic Foundations: 80% Modeling and Simulation: 20%