The analysis of PMHSS-multigrid methods for elliptic problems with smooth complex coefficients

In this paper, we investigate a class of multigrid methods with HSS smoothers applied to second order elliptic problems whose dominant coefficient is complex valued. These smoothers are based on Hermitian/skew-Hermitian splitting (HSS), modified HSS (MHSS) and preconditioned MHSS (PMHSS) iterations. It is shown that the abstract theory for multigrid method can be extended and applied to elliptic problems with complex coefficient. Under some assumption conditions, we prove that multigrid method with PMHSS smoother is convergent and optimal. Numerical results are reported to confirm the theoretical analysis.