  We generalize the standard computation of homogeneous nucleation theory at
zero temperature to a scenario in which the bubble shape is determined
self-consistently with its quantum fluctuations. Studying two scalar models in
1+1 dimensions, we find the self-consistent bounce by employing a two-particle
irreducible (2PI) effective action in imaginary time at the level of the
Hartree approximation. We thus obtain an effective single bounce action which
determines the rate exponent. We use collective coordinates to account for the
translational invariance and the growth instability of the bubble and finally
present a new nucleation rate prefactor. We compare the results with those
obtained using the standard 1-loop approximation and show that the
self-consistent rate can differ by several orders of magnitude.
