Fast algorithm for matrix-vector multiply of asymmetric multilevel block-Toeplitz matrices in 3-D scattering

A new O(N log N) FFT-based method to expedite matrix-Vector multiplies involving multilevel block-Toeplitz (MBT) matrices is presented. The method is also a minimal memory method with O(N) memory requirements because only nonredundant entries of the MBT matrix are stored. The accuracy and convergence of the method are illustrated in the calculation of the scattered field and the effective permittivity of a sphere with size parameter ka up to 5 using a volume integral formulation akin to the discrete dipole approximation. (C) 2001 John Wiley & Sons, Inc.