  It has recently been established that a short-range interaction can strongly
delocalize a pair of particles moving in a disordered potential. We investigate
whether an analogous effect exists also for pairs of quasiparticles in the
Anderson insulator by employing an approximate numerical evaluation of the
two-particle Green function of the many-body system. At the Fermi energy, the
quasiparticle pair is localized on the scale of the single-particle
localization length. The delocalization effect is recovered when the excitation
energy of the pair is comparable to the bandwidth.
