  First order phase transitions in general proceed via nucleation of bubbles. A
theoretical basis for the calculation of the nucleation rate is given by the
homogeneous nucleation theory of Langer and its field theoretical version of
Callan and Coleman. We have calculated the nucleation rate beyond the thin wall
approximation by expanding the bubble solution and the fluctuation determinant
in powers of the asymmetry parameter. The result is expressed in terms of
physical model parameters.
