It is widely assumed that for the Electroweak Baryogenesis mechanism to
be effective in generating the baryon asymmetry of the Universe, the first
order phase transition bubbles have to expand at a subsonic speed (in order
to allow for the diffusion of CP asymmetric currents in front of the wall).
Here we present a new mechanism for Electroweak Baryogenesis that is effective
for supersonic bubble walls, and relies on the formation of small bubbles of
symmetric phase in the plasma behind the bubble wall (which is in the broken
phase) due to the heating of the plasma as the wall passes by.