Consider a domain $\Omega \subseteq \mathbb{R}^{2,3}$ which is non convex and with $C^2$ boundary. Could you recommend a good reference where it is explained how:
- without needing isoparametric elements
- with a triangulation of simplices
one can obtain:
- some space of linear finite elements $S^h_0$ which vanish on $\partial \Omega$ (the reference should clearly explain how to define the hat functions outside of $\Omega$ and what properties the triangulation should satisfy...)
- a suitable definition of the nodal interpolator $I_h:H^2(\Omega)\cap H^1_0(\Omega)\rightarrow S^h_0$
such that the approximation property $||I_hv-v||_{L^2}+h||\nabla(I_hv-v)||_{L^2}\leq C h^s , ||v||_{H^s}$ holds for $s=1,2$?