It has recently been shown that topological excitations of metastable phases such as non-Abelian monopoles can dissociate and decay through the radial expansion of the excitation core. In this paper it is indicated that, according to some grand unified field theories, the monopole dissociation process might occur in the early Universe. In particular, the case of an SU(5)-symmetric grand unified field theory which breaks spontaneously to SU(4)×U(1) symmetry and then to SU(3)×SU(2)×U(1) symmetry is studied, and it is demonstrated that monopoles that are created in the transition from SU(5) symmetry to SU(4)×U(1) symmetry generally dissociate after the SU(4)×U(1) phase becomes metastable with respect to the SU(3)×SU(2)×U(1) phase but before there is any significant spontaneous production of bubbles associated with barrier penetration from the SU(4)×U(1) phase to the SU(3)×SU(2)×U(1) phase. Thus, the monopole dissociation process does indeed occur in such models and the monopoles may act as seeds for the inhomogeneous phase transition from SU(4)×U(1) symmetry to SU(3)×SU(2)×U(1) symmetry. If the transition occurs inhomogeneously, the transition temperature is higher and less latent heat is released in the transition.

• Received 13 April 1981

DOI:https://doi.org/10.1103/PhysRevD.24.842