  We examine the Gross-Pitaevskii (GP) model for Bose-Einstein condensates in
parabolic traps with attractive interactions. The decay of metastable
condensates is investigated by applying the instanton formalism to the GP field
theory. Employing various dynamical trial states, we derive within a coherent
state path integral approach a collective coordinate description in terms of
the condensate radius, in agreement with (and extending) earlier results. We
then solve numerically for the complete instanton field configuration and
compare with the collective coordinate approach. Adjusting only the effective
mass of the collective coordinate, the two schemes are then in good agreement.
