  Using a toy model Lagrangian we investigate the formation of vortices in
first order phase transitions. The evolution and interactions of vacuum bubbles
are also studied using both analytical approximations and a numerical
simulation of scalar field dynamics. A long lived bubble wall bound state is
discovered and its existence is justified by using a simplified potential for
the bubble wall interaction. The conditions that need to be satisfied for
vortex formation by bubble collisions are also studied with particular emphasis
placed on geometrical considerations. These conditions are then implemented in
a Monte Carlo simulation for the study of the probability of defect formation.
It is shown that the probability of vortex formation by collision of
relativistically expanding bubbles gets reduced by about 10% due to the above
mentioned geometric effects.
