STABILITY OF Z-STRINGS IN STRONG MAGNETIC-FIELDS

We show that the Z strings of the standard electroweak theory can be s tabilized by Strong external magnetic fields, provided that beta(1/2) = M(H)/M(Z) less than or equal to 1, where M(H) and M(Z) are the Higgs and Z masses. The magnetic fields needed are larger than beta(1/2)B(c ), and smaller than B-c, where B-c = M(W)(2)/e is the critical magneti c field which causes W condensation in the usual broken phase vacuum. If such magnetic fields were present after the electroweak transition, they would stabilize strings for a period comparable to the inverse H ubble rate at that time. Pair creation of monopoles and antimonopoles linked by segments of string is briefly considered.