A wideband fast multipole method for the Helmholtz equation in three dimensions

We describe a wideband version of the Fast Multipole Method for the Helmholtz equation in three dimensions. It unifies previously existing versions of the FMM for high and low frequencies into an algorithm which is accurate and efficient for any frequency, having a CPU time of O(N) if low-frequency computations dominate, or O(N log N) if high-frequency computations dominate. The performance of the algorithm is illustrated with numerical examples.