Space–Time PML and Subgrid Connections for Finite Integration Method

The perfectly matched layer (PML) absorbing boundary is employed in the space-time finite integration (FI) method. Subgrid connections in the 3-D space-time and the 4-D space-time are considered. Using the PML, the computational accuracy for the 3-D and 4-D space-time subgrid methods are evaluated. The subgrid scheme given by the space-time FI method suppresses unphysical wave reflections compared with the subgrid scheme based on the spatial FI method.