False Vacuum Decay Seeded by Global Cosmic Strings

A complex scalar field caught in the false minimum of a potential may tunnel through the potential barrier and create a bubble expanding and converting all of space into the true vacuum. This phenomenon introduced by S. Coleman and C. Callan is reviewed with great care and then expanded upon. We consider a vacuum state containing a straight, global or local cosmic string. The core is occupied by the true vacuum which is separated by a thin cylindrical wall from the false vacuum in the exterior of the string core. This setup is modeled by a complex scalar field under a global or local U(1) symmetry with non-zero winding with a wine bottle potential of nearly degenerate minima. We compute the bounce action for a global-string-induced tunneling, where the string is destabilized locally developing an expanding lump that converts space into the true vacuum. This new bounce configuration has an O(2) x O(2) symmetry. We solve the bounce and the solution is then used to model the shape and trajectory of these elongated bubbles for a full range of parameter values. We compare the string induced tunneling to that of the Coleman bubble and describe the parameter range where the cosmic string bubbles dominate the transition rate.