A Pseudospectral Fictitious Point Method for High Order Initial-Boundary Value Problems

When pseudospectral approximations are used for space derivatives, one often encounters spurious eigenvalues. These can lead to severe time stepping difficulties for PDEs. This is especially the case for equations with high order derivatives in space, requiring multiple conditions at one or both boundaries. We note here that a very simple-to-implement fictitious point approach circumvents most of these difficulties. The new approach is tested on the Kuramoto-Sivashinsky equation and on a dispersive linear PDE featuring a time-space corner singularity.