Corrections: Multi-Grid Methods for Saddle Point Systems using Constrained Smoothers

paper

Typos

• In page 2863, line 18 and 29, and page 2865, line 9 and -17, the fractional norm $\|| (I - P_H) u_h \||_{s}$ should be replaced by $\| (I - P_H) u_h \|_s$.
• In page 2865, line -5: for the sup, $\rho\in H^{\alpha-1}$ not $H^{1-\alpha}$.

Presentation

• Lemma 6.1. The $L^2$ projection $Q_{\mathcal K}: \mathcal V \to \mathcal K$ is stable in the fraction norm in the sense that: for any $s\in [0,1]$, there exists a constant $C_s$ such that $$\|| Q_{\mathcal K}v \||_s \leq C_s\|v\|_s, \quad \forall v\in \mathcal V.$$