Lower bound on the electroweak wall velocity from hydrodynamic instability

Understand

The subsonic expansion of bubbles in a strongly first-order electroweak phase transition is a convenient scenario for electroweak baryogenesis.

• For most extensions of the Standard Model, stationary subsonic solutions (i.e., deflagrations) exist for the propagation of phase transition fronts.
• However, deflagrations are known to be hydrodynamically unstable for wall velocities below a certain critical value.
• We calculate this critical velocity for several extensions of the Standard Model and compare with an estimation of the wall velocity.