Effect of strong magnetic field on the first-order electroweak phase   transition
  The broken-symmetry electroweak vacuum is destabilized in the presence of a magnetic field stronger than a critical value. Such magnetic field may be generated in the phase transition and restore the symmetry inside the bubbles. A numerical calculation indicates that the first-order phase transition is delayed but may be completed for a sufficient low value of the Higgs mass unless the magnetic field is extremely high. 
R. Fiore, A. Tiesi, L. Masperi and A. Megevand