Dynamical theory of phase transitions and topological defect formation in the early universe

摘要

We review the current issues of noncquilibriuni phase transitions, in particular, in (he early universe. Phase transitions cannot maintain thermal equilibrium and get nonequilibrium when t he thermal relaxation time scale is greater than the dynamical time scale. Nonequilibrium plia.se tra.iisi1.ions would have happened in certain evolution stages of the early universe because the rapid expansion quenched matter fields. We apply the recently introduced Liouville-von Neumann method, another canonical method, to nonequilibrium phase transitions in the Minkowski space-time and find the scaling behavior of domain sizes. Topological defects are thus determined by the dynamical processes of noncquilibrium phase transitions. However, the expansion of the universe freezes domain growth in the comoving frame and thus leads to a scale-invariant domain size. We also discuss the physical implications of nonequilibrium phase transitions in the early universe.