  In brane world scenarios the Friedmann equation is modified, resulting in an
increased expansion at early times. This has important effects on cosmological
phase transitions which we investigate, elucidating significant differences to
the standard case. First order phase transitions require a higher nucleation
rate to complete; baryogenesis and particle abundances could be suppressed.
Topological defect evolution is also affected, though the current defect
densities are largely unchanged. In particular, the increased expansion does
not solve the usual monopole and domain wall problems.
