Pointwise gradient estimate of the ritz projection

Lars Diening, Julian Rolfes, Abner J. Salgado

Let $\Omega \subset {\mathbb{R}}^n$ be a convex polytope ($n\le 3$). The Ritz projection is the best approximation, in the $W_0^{1,2}$-norm, to a given function in a finite element space…