COSMIC-STRING ZERO MODES AND MULTIPLE PHASE-TRANSITIONS

The zero modes and current carrying capability of a cosmic string form ed at one phase transition can be modified at subsequent phase transit ions. A new, generalised index theorem is derived that is applicable t o theories with multiple phase transitions, This enables us to investi gate the fate of string zero modes during sequences of phase transitio ns in a variety of models. Depending on the couplings that the breakin g introduces, the zero modes may be destroyed and the superconductivit y of the string removed, and thus vortons dissipate. We discuss the fe atures of the theory that are required to produce this behaviour and c onsider the implications of spectral flow. (C) 1997 Elsevier Science B .V.