In first-order phase transitions in the early universe, the bubble wall is
expected to be significantly slowed-down by its interaction with the
surrounding plasma. We examine the behaviour of the phase of the Higgs field
after two-bubble collisions, and find that phase differences equilibrate much
more quickly in slow-moving bubbles than in those which expand at the speed of
light. This could lead to a significant reduction in the initial density of
topological defects formed at a first-order phase transition.Comment: 4 pages, 2 figures, to appear in Proceedings of the International
Workshop on Particle Physics and the Early Universe (COSMO 99), Trieste,
Italy, September 27 - October 2, 199
